替换数组内容的简单方法 [英] Short way to replace content of an array
问题描述
有没有什么方便的方法来替换数组的内容，并保留对它的引用?我不想像这样替换数组:
Is there any convenient way to replace the content of an array, AND keep a reference to it? I don't want to replace the array like this:
var arr1 = [1,2,3];
var referenceToArr1 = arr1;
var arr2 = [4,5,6];
arr1 = arr2;
// logs: [4,5,6] false
console.log(arr1, arr1===referenceToArr1);
// logs [1,2,3]
console.log(referenceToArr1);
这种方式arr1有arr2的内容，但是我在referenceToArr1中丢失了引用，因为它仍然指向原文 arr1.
This way arr1 has the content of arr2, but I loose the reference in referenceToArr1, because it still points to the original arr1.
通过这种方式，我不会丢失引用:
With this way, I don't loose the reference:
var arr1 = [1,2,3];
var referenceToArr1 = arr1;
var arr2 = [4,5,6];
arr1.length = 0;
for (var i = 0; i < arr2.length; i++) {
arr1.push(arr2[i]);
}
// logs: [4,5,6] true
console.log(arr1, arr1===referenceToArr1);
// logs: [4,5,6]
console.log(referenceToArr1)
这里的缺点是，我必须清空 arr1.length = 0，遍历 arr2 的每个元素并将其推送到 arr1> 手动.
The drawback here is, that I have to empty arr1.length = 0, iterate over every element of arr2 and push it to arr1 by hand.
我的问题是:
- 当然，我可以为此编写一个帮助程序，但最有效的方法是什么?
- 是否有一种简短的、原生的 javascript 方法来执行此操作(也许是单行?)
- 我也在使用 underscore.js，但还没有找到解决此类问题的方法.有没有办法用 underscore.js 做到这一点?
背景:
我有一个带有服务的 AngularJS 应用程序.在这个服务中，我有一个数组来保存从服务器加载的所有元素.来自服务 get 的数据绑定到控制器并在视图中使用.当来自服务的数据发生变化时(例如发生重新获取)，我想自动更新我的控制器变量和它绑定到的视图.
I have an AngularJS app with a service. Inside this service, I have an array to keep all the elements loaded from the server. The data from the service get's bind to a controller and is used in a view. When the data from the service get's change (e.g. a refetch happens), I want to auto update my controllers vars and the view it is bind to.
这是一个 Plunker:http://plnkr.co/edit/8yYahwDO6pAuwl6lcpAS?p=预览
var app = angular.module('plunker', []);
app.controller('MainCtrl', function($scope, myService) {
$scope.name = 'World';
myService.fetchData().then(function(data) {
console.log(data)
$scope.data = data;
})
});
app.service('myService', function($timeout, $q) {
var arr;
var deferred;
var loadData = function() {
// here comes some data from the server
var serverData = [1,2,3];
arr = serverData;
deferred.resolve(arr);
// simulate a refetch of the data
$timeout(function() {
var newServerData = [4,5,6];
// this won't work, because MainCtrl looses it's reference
// arr = newServerData;
}, 1000);
$timeout(function() {
var newServerData = [7,8,9];
arr.length = 0;
[].push.apply(arr, newServerData);
}, 2000);
$timeout(function() {
var newServerData = [10,11,12];
[].splice.apply(arr, [0, arr.length].concat(newServerData));
}, 3000);
}
return {
fetchData: function() {
deferred = $q.defer();
loadData();
return deferred.promise;
}
}
})
和视图:
<!DOCTYPE html>
<html ng-app="plunker">
<head>
<meta charset="utf-8" />
<title>AngularJS Plunker</title>
<script>document.write('<base href="' + document.location + '" />');</script>
<link rel="stylesheet" href="style.css" />
<script data-require="angular.js@1.2.x" src="https://code.angularjs.org/1.2.16/angular.js" data-semver="1.2.16"></script>
<script src="app.js"></script>
</head>
<body ng-controller="MainCtrl">
<ul>
<li ng-repeat="d in data">{{d}}</li>
</ul>
3 refetches every second
</body>
</html>
推荐答案
这个怎么样:
// 1. reset the array while keeping its reference
arr1.length = 0;
// 2. fill the first array with items from the second
[].push.apply(arr1, arr2);
见:
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