string multireplace not regexp

replace.js

function replaceSubstring(inSource, inToReplace, inReplaceWith) {
    var outString = [];
    var repLen = inToReplace.length;
    var idx = inSource.indexOf(inToReplace);
    while (idx !== -1) {
        outString.push(inSource.substring(0, idx))
        outString.push(inReplaceWith);

        inSource = inSource.substring(idx + repLen);
        idx = inSource.indexOf(inToReplace);
    }
    outString.push(inSource);
    return outString.join("");
}