Remove string characters from a string if not matched in an array

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soum

I am trying to loop over an array which contains strings that I want my input string to compare with. So approach is I am looping over an input string to check if each character matches with one of the elements present in the array. If not just replace that character with just ''. Note: regular expression is really not an option.

Here is how my JavaScript looks like

var input = 'this is A [{}].-_+~`:; *6^123@#$%&*()?{}|\ ';
input.toLowerCase(input)

var allowed = ['0','1','2','3','4','5','6','7','8','9','a','b','c','d', 'e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','s','à','â','ä','è','é','ê','ë','î','ï','ô','œ','ù','û','ü','ÿ','ç','À','Â','Ä','È','É','Ê','Ë','Î','Ï','Ô','Œ','Ù','Û','Ü','Ÿ','Ç', ' '] 

var cleanStr = '';
for(var i = 0; i < input.length; i++){
    for(var j = 0; j< allowed.length; j++){
    if(input[i] !== allowed[j]){
        cleanStr = input.replace(input[i], ' ');
      console.log(cleanStr);
    }
  }
}

The console log output doesn't appear to be any different than the input field. What am I missing?

Here is my fiddle

https://jsfiddle.net/sghoush1/nvnk7r9j/4/

Tushar

You can do this in a single loop.

var input = 'this is A [{}].-_+~`:; *6^123@#$%&*()?{}|\ ';
input = input.toLowerCase(); // Note the syntax here

var allowed = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'à', 'â', 'ä', 'è', 'é', 'ê', 'ë', 'î', 'ï', 'ô', 'œ', 'ù', 'û', 'ü', 'ÿ', 'ç', 'À', 'Â', 'Ä', 'È', 'É', 'Ê', 'Ë', 'Î', 'Ï', 'Ô', 'Œ', 'Ù', 'Û', 'Ü', 'Ÿ', 'Ç', ' '];

var cleanStr = '';

// Loop over each character in the string
for (var i = 0; i<input.length; i++) {

    // Check if the character is allowed or not
    if (allowed.indexOf(input[i]) !== -1) {
        // Concat the allowed character to result string
        cleanStr += input[i];
    }
}

console.log(cleanStr);
document.body.innerHTML = cleanStr;

RegEx Approach:

You can create RegEx from a string using the RegExp constructor. To replace non-allowed characters, negated character class RegEx can be used.

var regex = new RegExp('[^' + allowed.join('') + ']', 'g');
var cleanStr = input.replace(regex, '');

Note: You'll need to escape meta-characters that have special meaning in the Character class.

Meta-characters that are needed to escape by preceding backslash \ in the character class^{Quoting from www.regular-expressions.info}.

In most regex flavors, the only special characters or metacharacters inside a character class are the closing bracket (]), the backslash (\), the caret (^), and the hyphen (-).

var input = 'this is A [{}].-_+~`:; *6^123@#$%&*()?{}|\ ';
var allowed = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 's', 'à', 'â', 'ä', 'è', 'é', 'ê', 'ë', 'î', 'ï', 'ô', 'œ', 'ù', 'û', 'ü', 'ÿ', 'ç', 'À', 'Â', 'Ä', 'È', 'É', 'Ê', 'Ë', 'Î', 'Ï', 'Ô', 'Œ', 'Ù', 'Û', 'Ü', 'Ÿ', 'Ç', ' '];

var regex = new RegExp('[^' + allowed.join('') + ']', 'gi');
console.log(regex);

var cleanStr = input.replace(regex, '');
console.log(cleanStr);

If the allowed characters array is fixed, you can use following RegEx to replace the non-allowed characters. Also, there is no need to convert the string to lower-case, use i flag for case-insensitive match.

var regex = /[^0-9a-zàâäèéêëîïôœùûüÿç ]/gi;

RegEx101 Live Demo

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edited at2021-07-15

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