Question

I want to use the _.where underscore function but I can’t seem do get it to work on an array of objects. I have the following 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"}          
    ];

And then I am using the following code to add each to an array:

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

I am trying to use underscore to get items from the list as follows:

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

But I am getting the following script error:

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

EDIT
You could also use something like

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

Answer 1

_.where is only available in 1.4.0 http://underscorejs.org/#where

You have to use Varon’s suggestion with _.find

Or you can simply use JS https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/filter

Example: 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'
});