accessing n values from json objects in javascript

Question

var list=[
{
    color_1: "red",
    color_2: "red_1",
    value: "#f00"
},
{
    color_1: "green",
    color_2: "red_5",
    value: "#0f0"
},
{
    color_1: "blue",
    color_2: "red",
    value: "#00f"
},
{
    color_1: "cyan",
    color_2: "red",
    value: "#0ff"
},
{
    color_1: "magenta",
    color_2: "red",
    value: "#f0f"
},
{
    color_1: "yellow",
    color_2: "red",
    value: "#ff0"
},
{
    color_1: "black",
    color_2: "red",
    value: "#000"
}

];

in my json list i am getting dyanamic columns from back end like color_1,color_2,color_3,color_4....color_n upto n number of columns in json objects, i want to print them on console using for loop ,but i am getting undefined as output could you please tell me where i am getting wrong below is code

function callMe(){

    list.forEach(function(element, i) {
    for(var j=1;j<3;j++){

            console.log(element.color_+j);
        }
    });
}

score 1 · Answer 1 · answered Feb 08 '20 at 17:06

You need a proper property accessor with brackets and a string.

console.log(element['color_' + j]);

function callMe() {
    list.forEach(function(element, i) {
        for (var j = 1; j < 3; j++) {           // var instead of int
            console.log(element['color_' + j]); // brackets
        }
    });
}

var list = [{ color_1: "red", color_2: "red_1", value: "#f00" }, { color_1: "green", color_2: "red_5", value: "#0f0" }, { color_1: "blue", color_2: "red", value: "#00f" }, { color_1: "cyan", color_2: "red", value: "#0ff" }, { color_1: "magenta", color_2: "red", value: "#f0f" }, { color_1: "yellow", color_2: "red", value: "#ff0" }, { color_1: "black", color_2: "red", value: "#000" }];

callMe();

.as-console-wrapper { max-height: 100% !important; top: 0; }

Danyman · Answer 2 · 2020-02-08T17:07:46.480

0

I would use console.log(element["color_"+j])

Hope that helps!

edited Feb 08 '20 at 17:07

answered Feb 08 '20 at 17:05

Danyman

63
1
9

typo ! `console.log(element["color_"+j])` (no dot) – Pierre Feb 08 '20 at 17:06
right thanks Pierre – Danyman Feb 08 '20 at 17:07

score 0 · Answer 3 · answered Feb 08 '20 at 17:09

0

To access an entry with a computed key you should use square brackets like this:

console.log(element[“color_”+j]);

The way you tried first gets element.color_ which is undefined, then adds j to undefined.

answered Feb 08 '20 at 17:09

Always Learning

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accessing n values from json objects in javascript

3 Answers3