How do I delete a value from an object based on criteria in javaScript

Question

Why does this code run without errors, but not delete anything from obj?

function removeEvenValues(obj) {
       for (i=0; i < obj.length;++i)
          if (obj[i].value%2===0)
            delete obj[i];
            return obj;
}

const obj = {a:1, b:2 ,c:3, d:4}
const res = removeEvenValues(obj);

console.log(res);

Because the way you are iterating over object is incorrect!!. If your obj is an array then access elements like obj[i].value. To iterate over object use for key in obj — Mukesh Verma
– Mukesh Verma, Commented Oct 22, 2018 at 20:34
What is the type of obj? from the snippet, it doesn't look like an array and hence you can't loop. Did you mean if (obj[i].value%2===2)? — vijay krishna
– vijay krishna, Commented Oct 22, 2018 at 20:36
Please edit the question to include an example of obj it's really difficult to help if we don't know what that looks like. — Mark
– Mark, Commented Oct 22, 2018 at 20:37
Your obj is not avid javascript. Is it supposed to be: obj ={a:1,b:2,c:3,d:4}? — Mark
– Mark, Commented Oct 22, 2018 at 20:40

Mark · Accepted Answer · 2018-10-22 20:50:45Z

1

Unlike Python you can't just iterate the length of an object because obj.length === undefined. You can use Object.keys() to get an array of keys. Then you can iterate them:

obj = {a:1,b:2,c:3,d:4}

function removeEvenValues(obj) {
       Object.keys(obj).forEach(key =>{
        if (obj[key] % 2 ===0)
            delete obj[key];
       })  
       return obj;
}

console.log(removeEvenValues(obj))

or you can also use for...in:

obj = {a:1,b:2,c:3,d:4}

function removeEvenValues(obj) {
   for(let key in obj){
     if (obj[key] % 2 ===0)
         delete obj[key];
     }
     return obj
}

console.log(removeEvenValues(obj))

edited Oct 22, 2018 at 20:50

answered Oct 22, 2018 at 20:42

Mark

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2 Comments

Guar Over a year ago

Is for (i = 0; i < obj.length; ++i) not a preferred method anymore in jS?

Mark Over a year ago

@Guar for loops are fine. The problem is that objects don't have a length. obj.length === undefined.

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