两个二维数组比较，求不同项

Question

var $a=[{id:1,name:"a"},{id:2,name:"b"},{id:3,name:"c"},{id:4,name:"d"}],
$b=[{id:1,name:"a"},{id:2,name:"b"},{id:3,name:"c"},{id:4,name:"d"},{id:5,name:"e"},{id:6,name:"f"},{id:7,name:"g"},{id:8,name:"h"}];
有两个二维数组，分别是$a和$b，找出两个数组的不同项。
求以最高性能快速解出！

Answer 1

var $a=[{id:1,name:"a"},{id:2,name:"b"},{id:3,name:"c"},{id:4,name:"d"}],
    $b=[{id:1,name:"a"},{id:2,name:"b"},{id:3,name:"c"},{id:4,name:"d"},{id:5,name:"e"},{id:6,name:"f"},{id:7,name:"g"},{id:8,name:"h"}];

console.table( array_diff($a, $b) );

function array_diff(a, b) {
    return diff(a, b).concat( diff(b, a) );
    function diff(a, b) {
        var c = {};
        b.forEach(function(o){ c[ JSON.stringify(o) ] = 0 });
        a.forEach(function(o){ delete c[ JSON.stringify(o) ]; });
        return Object.keys(c).map(JSON.parse);
    }
}

Answer 2

a,b分别排序后遍历比较

http://underscorejs.org/#isEqual