javascript - example regexp replace() method equivalent (with lastindex support)

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// Note: in the snippet you can find missing `RexExp.prototype.replace()` method equivalent that
//       supports `RexExp.prototype.lastIndex` property.

// Hint: this approach may be used in the web borsers where 'y' flag is not working with
//       `String.prototype.replace()` method in the proper way (where `RexExp.prototype.lastIndex` is ignored).

const replaceText = (expression, text, replacer) => {
    const global = expression.global;
    let index = 0;
    let result = '';
    while (true) {
        const match = expression.exec(text);
        if (match === null) {
            break;
        }
        const entry = match[0];
        result += text.substring(index, match.index);
        result += replacer(...match);
        index = match.index + entry.length;
        if (global === false) {
            break;
        }
    }
    result += text.substring(index, text.length);
    return result;
};


// Usage example:

const expression = /bc/g;
const text = 'abcd+abcd';

console.log(replaceText(expression, text, (match) => '<--REPLACEMENT-->'));  // a<--REPLACEMENT-->d+a<--REPLACEMENT-->d