Add new object to incoming json string

Question

I'm trying to parse an incoming json string and push a new object to that.

I've tried it like this:

addSetting(category) {
    console.log(category.value); //Console.log = [{"meta":"","value":""}]
    category.value = JSON.parse(category.value).push({meta: "", value: ""});
    console.log(category.value); //Console.log = 2
},

Problem is that category.value is 2? I would expect 2 json objects? What am I doing wrong here?

What you're doing by this category.value = JSON.parse(category.value).push({meta: "", value: ""}); is simply assigning the return value of the push operation to category.value which before now doesn't exist. — codejockie
– codejockie, Commented Oct 29, 2017 at 11:37

Paul K · Accepted Answer · 2017-10-29 11:47:39Z

1

Try:

addSetting(category) {
 category.value = JSON.parse(category.value);
 category.value.push({meta: "", value: ""});
 console.log(category.value);
}

You are using push() incorrectly. The array function push() returns the size of the new array.

Return value

The new length property of the object upon which the method was called.

ref:Array.prototype.push() MDN

As the new size of your array will be 2 (after pushing the new element) the following line was incorrect:

category.value = JSON.parse(category.value).push({meta: "", value: ""});

As after JSON was parsed, the variable category.value was assigned the return value of push.

edited Oct 29, 2017 at 11:47

answered Oct 29, 2017 at 11:37

Paul K

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