将json转换为下划线列表

Question

我想使用_.where下划线函数，但我似乎无法让它在一个对象数组上工作。我有以下json：

var Planets = [
        {name:"maths", percComp: "2", preReq: "english"},
        {name:"english", percComp: "20", preReq: "geog"},
        {name:"german", percComp: "20", preReq: "english"},
        {name:"history", percComp: "20", preReq: "german"},
        {name:"irish", percComp: "20", preReq: "geog"},
        {name:"geog", percComp: "20", preReq: ""},        
        {name:"french", percComp: "20", preReq: "spanish"},
        {name:"spanish", percComp: "57", preReq: "french"}          
    ];

然后我使用以下代码将每个代码添加到一个数组：

$(jQuery.parseJSON(JSON.stringify(Planets))).each(function(){
        var planet = new Class.Planet(this, paper);
        universe.push(planet);            
    });

我正在尝试使用下划线从列表中获取项目，如下所示：

var planets = _.where(universe, {name: "maths"});

但是我收到以下脚本错误：

Uncaught TypeError: Object function (a){return new j(a)} has no method 'where' 

编辑您也可以使用类似的东西

var planets = _.filter(Planets, function(p){ return p.name === "maths"});

Answer 1

_.where仅适用于1.4.0 http://underscorejs.org/#where

你必须使用Varon的建议与_.find

或者你可以简单地使用JS https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/filter

示例：http://jsfiddle.net/4mxjb/2/

// returns an array with objects where their name 
// property is equal to 'maths'
Planets.filter(function(obj){
    return obj.name === 'maths'
}); 

Answer 2

用下划线来获得这个星球

var planet = _.find(Planets, function(p) {return p.name == 'maths'});

Answer 3

只是为了清除旧答案中的混乱：

1. _.find 输入：比较功能 返回第一个匹配元素;
2. _.filter 输入：比较功能 返回所有匹配元素;
3. _.where 输入：对象 返回所有匹配元素;
4. _.findWhere 输入：对象 返回第一个匹配元素。

var Planets = [
    {name:"maths", percComp: "2", preReq: "english"},
    {name:"english", percComp: "20", preReq: "geog"},
    {name:"german", percComp: "20", preReq: "english"},
    {name:"history", percComp: "20", preReq: "german"},
    {name:"irish", percComp: "20", preReq: "geog"},
    {name:"geog", percComp: "20", preReq: ""},        
    {name:"french", percComp: "20", preReq: "spanish"},
    {name:"spanish", percComp: "57", preReq: "french"}        
];

console.log('---FIND---\n', // Returns only ONE matching element
  _.find(Planets, function(o){ return o.preReq === 'english'; })
);
console.log('---FILTER---\n', // Returns ALL matching elements
  _.filter(Planets, function(o){ return o.preReq === 'english'; })
);
console.log('---WHERE---\n', // Returns ALL matching elements
  _.where(Planets, {preReq: 'english'})
);
console.log('---FINDWHERE---\n', // Returns only ONE matching element
  _.findWhere(Planets, {preReq: 'english'})
);

<script
src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js">
</script>