javascript array find
// Use array.find() like this:
var myArrayOfAges = [1,4,6,8,9,13,16,21,53,78];
var result = myArrayOfAges.find(age => age >= 12);
console.log(result); // Output: 13
/* ------ Below is a polyfill from Mozilla: ------ */
// https://tc39.github.io/ecma262/#sec-array.prototype.find
if (!Array.prototype.find) {
Object.defineProperty(Array.prototype, 'find', {
value: function(predicate) {
// 1. Let O be ? ToObject(this value).
if (this == null) {
throw TypeError('"this" is null or not defined');
}
var o = Object(this);
// 2. Let len be ? ToLength(? Get(O, "length")).
var len = o.length >>> 0;
// 3. If IsCallable(predicate) is false, throw a TypeError exception.
if (typeof predicate !== 'function') {
throw TypeError('predicate must be a function');
}
// 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
var thisArg = arguments[1];
// 5. Let k be 0.
var k = 0;
// 6. Repeat, while k < len
while (k < len) {
// a. Let Pk be ! ToString(k).
// b. Let kValue be ? Get(O, Pk).
// c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
// d. If testResult is true, return kValue.
var kValue = o[k];
if (predicate.call(thisArg, kValue, k, o)) {
return kValue;
}
// e. Increase k by 1.
k++;
}
// 7. Return undefined.
return undefined;
},
configurable: true,
writable: true
});
}