JavaScript数组系列问题:数组差集

JavaScript求出两个数组的差集,下面是我实现的方法

function arrayDiffSet(a, b) {

    if ((!a || !a.length) && (b && b.length)) {
        return b
    } else if ((!b || !b.length) && (a && a.length)) {
        return a
    }

    var aMap = {},
        _aMap = {},
        _bMap = {};

    for (var i = 0, length = a.length; i < length; i++) {
        aMap[a[i]] = _aMap[a[i]] = true;
    }

    for (var i = 0, length = b.length; i < length; i++) {
        if (aMap[b[i]]) {
            delete _aMap[b[i]];
        } else {
            _bMap[b[i]] = true;
        }
    }

    return {
        a: Object.keys(_aMap),
        b: Object.keys(_bMap)
    }

}

function generateRandomArray(length, range) {
    var result = [];
    for (var i = 0; i < length; i++) {
        result[result.length] = Math.floor(Math.random() * range);
    }
    return result
}

var a = generateRandomArray(5, 10);
var b = generateRandomArray(10, 10);

console.log('a', a);
console.log('b', b);

console.time('start');
console.log(arrayDiffSet(a, b));
console.timeEnd('start');

----------但是这个方法还有下面两点:
1、扩展性差,如果我需要返回的差集不去重,那需要再重新写一个方法;
2、没有办法对对象数组求差集;

所以在这里想问问各位大神有没有更优的解决方案

阅读 1.8k
评论 更新于 2017-03-26
    2 个回答

    新方法:

    /**
     * 新方法
     * @param {Object} a
     * @param {Object} b
     * @param {Object} isDup 是否不去重(默认去重)
     */
    
    
    function arrayDiffSet(a, b, isDup) {
    
        var al = a.length,
            bl = b.length;
    
        if ((!a || !al) && (b && bl)) {
            return b
        } else if ((!b || !bl) && (a && al)) {
            return a
        }
    
        var i = 0,
            aMap = {},
            _aMap = {},
            _bMap = {},
            _a = [],
            _b = [],
            temp;
    
        for (i = 0; i < al; i++) {
            temp = a[i];
            aMap[temp] = true;
            !_aMap[temp] ? _aMap[temp] = [] : '';
            _aMap[temp][_aMap[temp].length] = temp;
        }
    
        for (i = 0; i < bl; i++) {
            temp = b[i];
            if (aMap[temp]) {
                delete _aMap[temp];
            } else {
                _b[_b.length] = temp;
                _bMap[temp] = true;
            }
        }
    
        if (isDup) {
            for (var item in _aMap) {
                _a = _a.concat(_aMap[item]);
            }
    
            return {
                a: _a,
                b: _b
            }
        }
    
        return {
            a: Object.keys(_aMap),
            b: Object.keys(_bMap)
        }
    
    }
    
    function generateRandomArray(length, range) {
        var result = [];
        for (var i = 0; i < length; i++) {
            result[result.length] = Math.floor(Math.random() * range);
        }
        return result
    }
    
    var a = generateRandomArray(1000, 1000);
    var b = generateRandomArray(1000, 1000);
    
    console.log(a);
    console.log(b);
    
    console.time('start');
    console.log(arrayDiffSet(a, b, true));
    console.timeEnd('start');
    

    另附:jQuery也是可以去重的
    var a = [1, 2, 3, 4];
    var b = [1, 2, 4, 5];
    var c = $(a).not(b);
    c = c.toArray(); // [3]

    评论 赞赏 2017-03-26