js数组操作

//合并arr1和arr2，并去重
var join = function(arr1, arr2) {
var dict = {};
arr1.concat(arr2).forEach(function(e) {
dict[e] = 1;
});
return Object.keys(dict);
}

//从arr1中去掉arr2中的所有元素
var filter = function(arr1, arr2) {
var dict = [];
arr1.forEach(function(e) { dict[e] = 1; });
arr2.forEach(function(e) { delete dict[e]; });
return Object.keys(dict);
}

var arr1 = [‘1’,’2’,’3’];
var arr2 = [‘2’,’3’,’4’]
console.log(join(arr1,arr2));
console.log(filter(arr1,arr2));