[源計劃] array-uniq

array-uniq

數組去重

來源

• GitHub

示例

const arrayUniq = require('array-uniq');

arrayUniq([1, 1, 2, 3, 3]);
//=> [1, 2, 3]

arrayUniq(['foo', 'foo', 'bar', 'foo']);
//=> ['foo', 'bar']

源碼

'use strict';

// there's 3 implementations written in increasing order of efficiency

// 1 - no Set type is defined
function uniqNoSet(arr) {
    var ret = [];

    for (var i = 0; i < arr.length; i++) {
        if (ret.indexOf(arr[i]) === -1) {
            ret.push(arr[i]);
        }
    }

    return ret;
}

// 2 - a simple Set type is defined
function uniqSet(arr) {
    var seen = new Set();
    return arr.filter(function (el) {
        if (!seen.has(el)) {
            seen.add(el);
            return true;
        }

        return false;
    });
}

// 3 - a standard Set type is defined and it has a forEach method
function uniqSetWithForEach(arr) {
    var ret = [];

    (new Set(arr)).forEach(function (el) {
        ret.push(el);
    });

    return ret;
}

// V8 currently has a broken implementation
// https://github.com/joyent/node/issues/8449
function doesForEachActuallyWork() {
    var ret = false;

    (new Set([true])).forEach(function (el) {
        ret = el;
    });

    return ret === true;
}

if ('Set' in global) {
    if (typeof Set.prototype.forEach === 'function' && doesForEachActuallyWork()) {
        module.exports = uniqSetWithForEach;
    } else {
        module.exports = uniqSet;
    }
} else {
    module.exports = uniqNoSet;
}