Async load inside replace function

Question

I am working with replacements in Javascript. I did something like this:

var replacedText = originalText.replace(regex, function(value, i) { 
    return valu         


        

Answer 1

No, replace does only support synchronous callbacks. However, here is a generic function that accepts a callback which yields promises, and returns a promise for the string with all replacements made:

function replaceAsync(str, re, callback) {
    // http://es5.github.io/#x15.5.4.11
    str = String(str);
    var parts = [],
        i = 0;
    if (Object.prototype.toString.call(re) == "[object RegExp]") {
        if (re.global)
            re.lastIndex = i;
        var m;
        while (m = re.exec(str)) {
            var args = m.concat([m.index, m.input]);
            parts.push(str.slice(i, m.index), callback.apply(null, args));
            i = re.lastIndex;
            if (!re.global)
                break; // for non-global regexes only take the first match
            if (m[0].length == 0)
                re.lastIndex++;
        }
    } else {
        re = String(re);
        i = str.indexOf(re);
        parts.push(str.slice(0, i), callback.apply(null, [re, i, str]));
        i += re.length;
    }
    parts.push(str.slice(i));
    return Promise.all(parts).then(function(strings) {
        return strings.join("");
    });
}