Array.prototype.includes()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2016.
Sumário
O método includes() determina se um array contém um determinado elemento, retornando true ou false apropriadamente.
Experimente
const array1 = [1, 2, 3]; console.log(array1.includes(2)); // Expected output: true const pets = ["cat", "dog", "bat"]; console.log(pets.includes("cat")); // Expected output: true console.log(pets.includes("at")); // Expected output: false Sintaxe
js
array.includes(searchElement[, fromIndex]) Parâmetros
searchElementO elemento a buscar
fromIndexOpcional. A posição no array de onde a busca pelo
searchElementse iniciará. Por padrão, 0.
Exemplos
js
[1, 2, 3].includes(2); // true [1, 2, 3].includes(4); // false [1, 2, 3].includes(3, 3); // false [1, 2, 3].includes(3, -1); // true [1, 2, NaN].includes(NaN); // true Polyfill
js
// https://tc39.github.io/ecma262/#sec-array.prototype.includes if (!Array.prototype.includes) { Object.defineProperty(Array.prototype, "includes", { value: function (searchElement, fromIndex) { // 1. Let O be ? ToObject(this value). if (this == null) { throw new 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 len is 0, return false. if (len === 0) { return false; } // 4. Let n be ? ToInteger(fromIndex). // (If fromIndex is undefined, this step produces the value 0.) var n = fromIndex | 0; // 5. If n ≥ 0, then // a. Let k be n. // 6. Else n < 0, // a. Let k be len + n. // b. If k < 0, let k be 0. var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0); // 7. Repeat, while k < len while (k < len) { // a. Let elementK be the result of ? Get(O, ! ToString(k)). // b. If SameValueZero(searchElement, elementK) is true, return true. // c. Increase k by 1. // NOTE: === provides the correct "SameValueZero" comparison needed here. if (o[k] === searchElement) { return true; } k++; } // 8. Return false return false; }, }); } 