我目前正在使用JavaScript库，为了减少错误数量，我认为我的库可能会受益于使用Dart的静态类型化机制。首先，因为我的库既没有与HTML也没有与其他JavaScript库进行任何互操作，所以仅是纯JavaScript对象操作之类的东西。但是我没有在网上找到任何信息显示如何使用dart构建JS库。所以我尝试自己做，创建了初始的dart文件：
library Repo;
class Type {
final String name;
final TypeCategory category;
Type(String name, TypeCategory category) : name = name, category = category {
category.types[name] = this;
}
}
class TypeCategory {
final String name;
final Map<String, Type> types = new Map();
TypeCategory(this.name);
}
class Branch {
}
class Descriptor {
}
class TableDescriptor extends Descriptor {
TableDescriptor.ctor() {
}
}
class Repo {
Descriptor descriptor(String name) {
}
Branch branch(String name) {
}
void Merge() {
}
}
main() {
return Repo;
}
使用dart2js将其编译为JavaScript，以查看我的状态：
// Generated by dart2js, the Dart to JavaScript compiler version: 1.3.6.
// The code supports the following hooks:
// dartPrint(message):
// if this function is defined it is called instead of the Dart [print]
// method.
//
// dartMainRunner(main, args):
// if this function is defined, the Dart [main] method will not be invoked
// directly. Instead, a closure that will invoke [main], and its arguments
// [args] is passed to [dartMainRunner].
(function($) {
function dart(){ this.x = 0 }var A = new dart;
delete A.x;
var B = new dart;
delete B.x;
var C = new dart;
delete C.x;
var D = new dart;
delete D.x;
var E = new dart;
delete E.x;
var F = new dart;
delete F.x;
var G = new dart;
delete G.x;
var H = new dart;
delete H.x;
var J = new dart;
delete J.x;
var K = new dart;
delete K.x;
var L = new dart;
delete L.x;
var M = new dart;
delete M.x;
var N = new dart;
delete N.x;
var O = new dart;
delete O.x;
var P = new dart;
delete P.x;
var Q = new dart;
delete Q.x;
var R = new dart;
delete R.x;
var S = new dart;
delete S.x;
var T = new dart;
delete T.x;
var U = new dart;
delete U.x;
var V = new dart;
delete V.x;
var W = new dart;
delete W.x;
var X = new dart;
delete X.x;
var Y = new dart;
delete Y.x;
var Z = new dart;
delete Z.x;
function Isolate() {}
init();
$ = Isolate.$isolateProperties;
var $$ = {};
(function (reflectionData) {
"use strict";
function map(x){x={x:x};delete x.x;return x}
function processStatics(descriptor) {
for (var property in descriptor) {
if (!hasOwnProperty.call(descriptor, property)) continue;
if (property === "^") continue;
var element = descriptor[property];
var firstChar = property.substring(0, 1);
var previousProperty;
if (firstChar === "+") {
mangledGlobalNames[previousProperty] = property.substring(1);
var flag = descriptor[property];
if (flag > 0) descriptor[previousProperty].$reflectable = flag;
if (element && element.length) init.typeInformation[previousProperty] = element;
} else if (firstChar === "@") {
property = property.substring(1);
$[property]["@"] = element;
} else if (firstChar === "*") {
globalObject[previousProperty].$defaultValues = element;
var optionalMethods = descriptor.$methodsWithOptionalArguments;
if (!optionalMethods) {
descriptor.$methodsWithOptionalArguments = optionalMethods = {}
}
optionalMethods[property] = previousProperty;
} else if (typeof element === "function") {
globalObject[previousProperty = property] = element;
functions.push(property);
init.globalFunctions[property] = element;
} else if (element.constructor === Array) {
addStubs(globalObject, element, property, true, descriptor, functions);
} else {
previousProperty = property;
var newDesc = {};
var previousProp;
for (var prop in element) {
if (!hasOwnProperty.call(element, prop)) continue;
firstChar = prop.substring(0, 1);
if (prop === "static") {
processStatics(init.statics[property] = element[prop]);
} else if (firstChar === "+") {
mangledNames[previousProp] = prop.substring(1);
var flag = element[prop];
if (flag > 0) element[previousProp].$reflectable = flag;
} else if (firstChar === "@" && prop !== "@") {
newDesc[prop.substring(1)]["@"] = element[prop];
} else if (firstChar === "*") {
newDesc[previousProp].$defaultValues = element[prop];
var optionalMethods = newDesc.$methodsWithOptionalArguments;
if (!optionalMethods) {
newDesc.$methodsWithOptionalArguments = optionalMethods={}
}
optionalMethods[prop] = previousProp;
} else {
var elem = element[prop];
if (prop !== "^" && elem != null && elem.constructor === Array && prop !== "<>") {
addStubs(newDesc, elem, prop, false, element, []);
} else {
newDesc[previousProp = prop] = elem;
}
}
}
$$[property] = [globalObject, newDesc];
classes.push(property);
}
}
}
function addStubs(descriptor, array, name, isStatic, originalDescriptor, functions) {
var f, funcs = [originalDescriptor[name] = descriptor[name] = f = array[0]];
f.$stubName = name;
functions.push(name);
for (var index = 0; index < array.length; index += 2) {
f = array[index + 1];
if (typeof f != "function") break;
f.$stubName = array[index + 2];
funcs.push(f);
if (f.$stubName) {
originalDescriptor[f.$stubName] = descriptor[f.$stubName] = f;
functions.push(f.$stubName);
}
}
for (var i = 0; i < funcs.length; index++, i++) {
funcs[i].$callName = array[index + 1];
}
var getterStubName = array[++index];
array = array.slice(++index);
var requiredParameterInfo = array[0];
var requiredParameterCount = requiredParameterInfo >> 1;
var isAccessor = (requiredParameterInfo & 1) === 1;
var isSetter = requiredParameterInfo === 3;
var isGetter = requiredParameterInfo === 1;
var optionalParameterInfo = array[1];
var optionalParameterCount = optionalParameterInfo >> 1;
var optionalParametersAreNamed = (optionalParameterInfo & 1) === 1;
var isIntercepted = requiredParameterCount + optionalParameterCount != funcs[0].length;
var functionTypeIndex = array[2];
var unmangledNameIndex = 2 * optionalParameterCount + requiredParameterCount + 3;
var isReflectable = array.length > unmangledNameIndex;
if (getterStubName) {
f = tearOff(funcs, array, isStatic, name, isIntercepted);
f.getterStub = true;
if (isStatic) init.globalFunctions[name] = f;
originalDescriptor[getterStubName] = descriptor[getterStubName] = f;
funcs.push(f);
if (getterStubName) functions.push(getterStubName);
f.$stubName = getterStubName;
f.$callName = null;
if (isIntercepted) init.interceptedNames[getterStubName] = true;
}
if (isReflectable) {
for (var i = 0; i < funcs.length; i++) {
funcs[i].$reflectable = 1;
funcs[i].$reflectionInfo = array;
}
var mangledNames = isStatic ? init.mangledGlobalNames : init.mangledNames;
var unmangledName = array[unmangledNameIndex];
var reflectionName = unmangledName;
if (getterStubName) mangledNames[getterStubName] = reflectionName;
if (isSetter) {
reflectionName += "=";
} else if (!isGetter) {
reflectionName += ":" + requiredParameterCount + ":" + optionalParameterCount;
}
mangledNames[name] = reflectionName;
funcs[0].$reflectionName = reflectionName;
funcs[0].$metadataIndex = unmangledNameIndex + 1;
if (optionalParameterCount) descriptor[unmangledName + "*"] = funcs[0];
}
}
function tearOffGetterNoCsp(funcs, reflectionInfo, name, isIntercepted) {
return isIntercepted
? new Function("funcs", "reflectionInfo", "name", "H", "c",
"return function tearOff_" + name + (functionCounter++)+ "(x) {" +
"if (c === null) c = H.closureFromTearOff(" +
"this, funcs, reflectionInfo, false, [x], name);" +
"return new c(this, funcs[0], x, name);" +
"}")(funcs, reflectionInfo, name, H, null)
: new Function("funcs", "reflectionInfo", "name", "H", "c",
"return function tearOff_" + name + (functionCounter++)+ "() {" +
"if (c === null) c = H.closureFromTearOff(" +
"this, funcs, reflectionInfo, false, [], name);" +
"return new c(this, funcs[0], null, name);" +
"}")(funcs, reflectionInfo, name, H, null)
}
function tearOffGetterCsp(funcs, reflectionInfo, name, isIntercepted) {
var cache = null;
return isIntercepted
? function(x) {
if (cache === null) cache = H.closureFromTearOff(this, funcs, reflectionInfo, false, [x], name);
return new cache(this, funcs[0], x, name)
}
: function() {
if (cache === null) cache = H.closureFromTearOff(this, funcs, reflectionInfo, false, [], name);
return new cache(this, funcs[0], null, name)
}
}
function tearOff(funcs, reflectionInfo, isStatic, name, isIntercepted) {
var cache;
return isStatic
? function() {
if (cache === void 0) cache = H.closureFromTearOff(this, funcs, reflectionInfo, true, [], name).prototype;
return cache;
}
: tearOffGetter(funcs, reflectionInfo, name, isIntercepted);
}
var functionCounter = 0;
var tearOffGetter = (typeof dart_precompiled == "function")
? tearOffGetterCsp : tearOffGetterNoCsp;
if (!init.libraries) init.libraries = [];
if (!init.mangledNames) init.mangledNames = map();
if (!init.mangledGlobalNames) init.mangledGlobalNames = map();
if (!init.statics) init.statics = map();
if (!init.typeInformation) init.typeInformation = map();
if (!init.globalFunctions) init.globalFunctions = map();
if (!init.interceptedNames) init.interceptedNames = map();
var libraries = init.libraries;
var mangledNames = init.mangledNames;
var mangledGlobalNames = init.mangledGlobalNames;
var hasOwnProperty = Object.prototype.hasOwnProperty;
var length = reflectionData.length;
for (var i = 0; i < length; i++) {
var data = reflectionData[i];
var name = data[0];
var uri = data[1];
var metadata = data[2];
var globalObject = data[3];
var descriptor = data[4];
var isRoot = !!data[5];
var fields = descriptor && descriptor["^"];
var classes = [];
var functions = [];
processStatics(descriptor);
libraries.push([name, uri, classes, functions, metadata, fields, isRoot,
globalObject]);
}
})
([
["Repo", "repo.dart", , F, {
"^": "",
main: function() {
return C.Type_Jeh;
}
},
1],
["_js_helper", "dart:_js_helper", , H, {
"^": "",
createRuntimeType: function($name) {
return new H.TypeImpl($name, null);
},
TypeImpl: {
"^": "Object;_typeName,_unmangledName"
}
}],
["dart.core", "dart:core", , P, {
"^": "",
Null: {
"^": "Object;"
},
Object: {
"^": ";"
}
}],
]);
Isolate.$finishClasses($$, $, null);
$$ = null;
// Runtime type support
// getInterceptor methods
C.Type_Jeh = H.createRuntimeType('Repo');
$.libraries_to_load = {};
$.Closure_functionCounter = 0;
$.BoundClosure_selfFieldNameCache = null;
$.BoundClosure_receiverFieldNameCache = null;
init.functionAliases = {};
;
init.metadata = [];
$ = null;
Isolate = Isolate.$finishIsolateConstructor(Isolate);
$ = new Isolate();
function convertToFastObject(properties) {
function MyClass() {};
MyClass.prototype = properties;
new MyClass();
return properties;
}
A = convertToFastObject(A);
B = convertToFastObject(B);
C = convertToFastObject(C);
D = convertToFastObject(D);
E = convertToFastObject(E);
F = convertToFastObject(F);
G = convertToFastObject(G);
H = convertToFastObject(H);
J = convertToFastObject(J);
K = convertToFastObject(K);
L = convertToFastObject(L);
M = convertToFastObject(M);
N = convertToFastObject(N);
O = convertToFastObject(O);
P = convertToFastObject(P);
Q = convertToFastObject(Q);
R = convertToFastObject(R);
S = convertToFastObject(S);
T = convertToFastObject(T);
U = convertToFastObject(U);
V = convertToFastObject(V);
W = convertToFastObject(W);
X = convertToFastObject(X);
Y = convertToFastObject(Y);
Z = convertToFastObject(Z);
// BEGIN invoke [main].
;(function (callback) {
if (typeof document === "undefined") {
callback(null);
return;
}
if (document.currentScript) {
callback(document.currentScript);
return;
}
var scripts = document.scripts;
function onLoad(event) {
for (var i = 0; i < scripts.length; ++i) {
scripts[i].removeEventListener("load", onLoad, false);
}
callback(event.target);
}
for (var i = 0; i < scripts.length; ++i) {
scripts[i].addEventListener("load", onLoad, false);
}
})(function(currentScript) {
init.currentScript = currentScript;
if (typeof dartMainRunner === "function") {
dartMainRunner(F.main, []);
} else {
F.main([]);
}
});
// END invoke [main].
function init() {
Isolate.$isolateProperties = {};
function generateAccessor(fieldDescriptor, accessors, cls) {
var fieldInformation = fieldDescriptor.split("-");
var field = fieldInformation[0];
var len = field.length;
var code = field.charCodeAt(len - 1);
var reflectable;
if (fieldInformation.length > 1)
reflectable = true;
else
reflectable = false;
code = code >= 60 && code <= 64 ? code - 59 : code >= 123 && code <= 126 ? code - 117 : code >= 37 && code <= 43 ? code - 27 : 0;
if (code) {
var getterCode = code & 3;
var setterCode = code >> 2;
var accessorName = field = field.substring(0, len - 1);
var divider = field.indexOf(":");
if (divider > 0) {
accessorName = field.substring(0, divider);
field = field.substring(divider + 1);
}
if (getterCode) {
var args = getterCode & 2 ? "receiver" : "";
var receiver = getterCode & 1 ? "this" : "receiver";
var body = "return " + receiver + "." + field;
var property = cls + ".prototype.get$" + accessorName + "=";
var fn = "function(" + args + "){" + body + "}";
if (reflectable)
accessors.push(property + "$reflectable(" + fn + ");\n");
else
accessors.push(property + fn + ";\n");
}
if (setterCode) {
var args = setterCode & 2 ? "receiver, value" : "value";
var receiver = setterCode & 1 ? "this" : "receiver";
var body = receiver + "." + field + " = value";
var property = cls + ".prototype.set$" + accessorName + "=";
var fn = "function(" + args + "){" + body + "}";
if (reflectable)
accessors.push(property + "$reflectable(" + fn + ");\n");
else
accessors.push(property + fn + ";\n");
}
}
return field;
}
Isolate.$isolateProperties.$generateAccessor = generateAccessor;
function defineClass(name, cls, fields) {
var accessors = [];
var str = "function " + cls + "(";
var body = "";
for (var i = 0; i < fields.length; i++) {
if (i != 0)
str += ", ";
var field = generateAccessor(fields[i], accessors, cls);
var parameter = "parameter_" + field;
str += parameter;
body += "this." + field + " = " + parameter + ";\n";
}
str += ") {\n" + body + "}\n";
str += cls + ".builtin$cls=\"" + name + "\";\n";
str += "$desc=$collectedClasses." + cls + ";\n";
str += "if($desc instanceof Array) $desc = $desc[1];\n";
str += cls + ".prototype = $desc;\n";
if (typeof defineClass.name != "string") {
str += cls + ".name=\"" + cls + "\";\n";
}
str += accessors.join("");
return str;
}
var inheritFrom = function() {
function tmp() {
}
var hasOwnProperty = Object.prototype.hasOwnProperty;
return function(constructor, superConstructor) {
tmp.prototype = superConstructor.prototype;
var object = new tmp();
var properties = constructor.prototype;
for (var member in properties)
if (hasOwnProperty.call(properties, member))
object[member] = properties[member];
object.constructor = constructor;
constructor.prototype = object;
return object;
};
}();
Isolate.$finishClasses = function(collectedClasses, isolateProperties, existingIsolateProperties) {
var pendingClasses = {};
if (!init.allClasses)
init.allClasses = {};
var allClasses = init.allClasses;
var hasOwnProperty = Object.prototype.hasOwnProperty;
if (typeof dart_precompiled == "function") {
var constructors = dart_precompiled(collectedClasses);
} else {
var combinedConstructorFunction = "function $reflectable(fn){fn.$reflectable=1;return fn};\n" + "var $desc;\n";
var constructorsList = [];
}
for (var cls in collectedClasses) {
if (hasOwnProperty.call(collectedClasses, cls)) {
var desc = collectedClasses[cls];
if (desc instanceof Array)
desc = desc[1];
var classData = desc["^"], supr, name = cls, fields = classData;
if (typeof classData == "string") {
var split = classData.split("/");
if (split.length == 2) {
name = split[0];
fields = split[1];
}
}
var s = fields.split(";");
fields = s[1] == "" ? [] : s[1].split(",");
supr = s[0];
split = supr.split(":");
if (split.length == 2) {
supr = split[0];
var functionSignature = split[1];
if (functionSignature)
desc.$signature = function(s) {
return function() {
return init.metadata[s];
};
}(functionSignature);
}
if (typeof dart_precompiled != "function") {
combinedConstructorFunction += defineClass(name, cls, fields);
constructorsList.push(cls);
}
if (supr)
pendingClasses[cls] = supr;
}
}
if (typeof dart_precompiled != "function") {
combinedConstructorFunction += "return [\n " + constructorsList.join(",\n ") + "\n]";
var constructors = new Function("$collectedClasses", combinedConstructorFunction)(collectedClasses);
combinedConstructorFunction = null;
}
for (var i = 0; i < constructors.length; i++) {
var constructor = constructors[i];
var cls = constructor.name;
var desc = collectedClasses[cls];
var globalObject = isolateProperties;
if (desc instanceof Array) {
globalObject = desc[0] || isolateProperties;
desc = desc[1];
}
allClasses[cls] = constructor;
globalObject[cls] = constructor;
}
constructors = null;
var finishedClasses = {};
init.interceptorsByTag = Object.create(null);
init.leafTags = {};
function finishClass(cls) {
var hasOwnProperty = Object.prototype.hasOwnProperty;
if (hasOwnProperty.call(finishedClasses, cls))
return;
finishedClasses[cls] = true;
var superclass = pendingClasses[cls];
if (!superclass || typeof superclass != "string")
return;
finishClass(superclass);
var constructor = allClasses[cls];
var superConstructor = allClasses[superclass];
if (!superConstructor)
superConstructor = existingIsolateProperties[superclass];
var prototype = inheritFrom(constructor, superConstructor);
}
for (var cls in pendingClasses)
finishClass(cls);
};
Isolate.$lazy = function(prototype, staticName, fieldName, getterName, lazyValue) {
var sentinelUndefined = {};
var sentinelInProgress = {};
prototype[fieldName] = sentinelUndefined;
prototype[getterName] = function() {
var result = $[fieldName];
try {
if (result === sentinelUndefined) {
$[fieldName] = sentinelInProgress;
try {
result = $[fieldName] = lazyValue();
} finally {
if (result === sentinelUndefined) {
if ($[fieldName] === sentinelInProgress) {
$[fieldName] = null;
}
}
}
} else {
if (result === sentinelInProgress)
H.throwCyclicInit(staticName);
}
return result;
} finally {
$[getterName] = function() {
return this[fieldName];
};
}
};
};
Isolate.$finishIsolateConstructor = function(oldIsolate) {
var isolateProperties = oldIsolate.$isolateProperties;
function Isolate() {
var hasOwnProperty = Object.prototype.hasOwnProperty;
for (var staticName in isolateProperties)
if (hasOwnProperty.call(isolateProperties, staticName))
this[staticName] = isolateProperties[staticName];
function ForceEfficientMap() {
}
ForceEfficientMap.prototype = this;
new ForceEfficientMap();
}
Isolate.prototype = oldIsolate.prototype;
Isolate.prototype.constructor = Isolate;
Isolate.$isolateProperties = isolateProperties;
Isolate.$finishClasses = oldIsolate.$finishClasses;
return Isolate;
};
}
})()
//# sourceMappingURL=out.js.map
//@ sourceMappingURL=out.js.map
就是这样，我扔掉了Dart，因为我不知道该如何处理生成的JS文件，而且我对于保持生成的库接口整洁并与我正在使用的库接口相似，可能会花费大量时间使用JavaScript。
即使Dart支持此用例，但如果您以JavaScript开发人员为目标，我仍会坚持使用JavaScript。
@AlexandreArdhuin在对使用JavaScript公开Dart函数的答案中展示了如何使Dart函数可用于JavaScript。
在dart-js-interop下，有许多示例如何进行函数调用以及在Dart和JavaScript之间传递数据。
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我来说两句