Javascript accessing class variables from window object

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kaushal

I was wondering if it is possible to access foo from window.updateFoo() in the code below:

function f1 () {
    'use strict';
    this.x = {};
    this.x.foo = 0;

    window.updateFoo = function(val){
       this.x.foo = val;       // Obviously wrong since 'this' doesn't refer to f1 now. Uncaught TypeError: Cannot set property 'foo' of undefined 
    };
    window.updateFoo(20);      // Try changing the value of this.x.foo?
}

Scimonster

When you call window.updateFoo, it is called in the context of window. Your best option is to save this in a variable, and then use that in the function:

function f1 () {
    'use strict';
    this.x = {};                // Object for 'const' variables
    this.x.foo = 0;

    var _this = this;

    window.updateFoo = function(val){
       _this.x.foo = val;       // Use saved version
    };
    window.updateFoo(20);      // Try changing the value of this.x.foo?
}

The other option, but it will only work within f1, is to call updateFoo will a specific context:

window.updateFoo.call(this, 20);

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에서 수정2021-06-1

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