根据JavaScript中另一个“属性值”从数组中选择“属性值”

Question

I have an array like this.

var nodes = [{ID:"101", x:100, y:200}
        ,{ID:"102", x:200, y:200}
        ,{ID:"103", x:300, y:300}
        ,{ID:"104", x:200, y:300}];

I'd like to have a function which takes node's ID as input and return its (x,y). For example, the function coordinates(103) should read the array (nodes) and return x = 300, y = 300 when it's called. Any pointer is appreciated. Thanks :) This is what I have so far. It works but I'd like to know neater and tidier methods.

function coordinates(id){
    for (var i=0 in nodes){
        if(nodes[i].ID == id){
            return { x: nodes[i].x, y: nodes[i].y};
        }
    }
}
console.log(coordinates(102));

Answer 1

See comments inline:

Demo

 var nodes = [{ ID: "101", x: 100, y: 200 }, { ID: "102", x: 200, y: 200 }, { ID: "103", x: 300, y: 300 }, { ID: "104", x: 200, y: 300 }]; var noOfCord = nodes.length; var coordinates = function(id) { for (var i = 0; i < noOfCord; i++) { if (nodes[i].ID == id) { return { x: nodes[i].x, y: nodes[i].y }; } } } document.write(coordinates(103).x + ', ' + coordinates(103).y); 

Answer 2

You can use .filter , like so

 var nodes = [{ ID: "101", x: 100, y: 200 }, { ID: "102", x: 200, y: 200 }, { ID: "103", x: 300, y: 300 }, { ID: "104", x: 200, y: 300 }]; function coordinates(nodes, id) { var result = nodes.filter(function (el) { return +el.ID === id; }); if (result && result.length) { result = result[0]; return { x: result.x, y: result.y }; } return null; } console.log(coordinates(nodes, 103)); 

Answer 3

basically you're looking at something like this

var f = function(id){
    var match = nodes.filter(function(d){ 
        return d.ID === id; 
    })
    return match && match.length && {x: match[0].x, y:match[0].y} 
    || {x: undefined, y: undefined};
};

then f('101') outputs {x: 100, y:200} and if cannot find a match then it will output {x: undefined, y: undefined}

Answer 4

Using array filter , Try:

 function coordinates(id){ return nodes.filter(function(e){ return e.ID == id })[0] } var nodes=[{ID:"101",x:100,y:200},{ID:"102",x:200,y:200},{ID:"103",x:300,y:300},{ID:"104",x:200,y:300}]; var result = coordinates("103"); document.write("<pre>" + JSON.stringify(result, null, 3)); 

Answer 5

Brilliant solutions with concrete JavaScript have already been proposed by people here. So I propose another alternative using underscore.js , just in case you're curious.

function coordinates(id){
    var n = _.findWhere(nodes, {ID: id});
    return {x: n.x, y: n.y }
}