query js arrays with lambda expressions. i love them.

javascript lambda

Array.prototype.where =
    function (f) {
        var fn = f;
        if (typeof f == "string")
            if (( fn = lambda(fn) ) == null)
                throw "Syntax error in lambda string: " + f;
        var res = [];
        var l = this.length;
        var p = [0, 0, res];
        for (var i = 1; i < arguments.length; i++) p.push(arguments[i]);
        for (var i = 0; i < l; i++) {
            if (typeof this[i] == "undefined") continue;
            p[0] = this[i];
            p[1] = i;
            if (!!fn.apply(this, p)) res.push(this[i]);
        }
        return res;
    };


function lambda(l) {
    var fn = l.match(/\((.*)\)\s*=>\s*(.*)/);
    var p = [];
    var b = "";

    if (fn.length > 0) fn.shift();
    if (fn.length > 0) b = fn.pop();
    if (fn.length > 0) p = fn.pop()
        .replace(/^\s*|\s(?=\s)|\s*$|,/g, '').split(' ');

    // prepend a return if not already there.
    fn = ( ( !/\s*return\s+/.test(b) ) ? "return " : "" ) + b;

    p.push(fn);

    try {
        return Function.apply({}, p);
    }
    catch (e) {
        return null;
    }
}




///jsonData.data.where("( el, i, res, param ) => el.plan_type == param", record[0].raw.name)