Undefined object property in foreach loop

Question

Here's my code:

headersObj = {a: "a", b: "b", c: "c"};
headers = ["a", "b", "c"];
fields = ["a", "b"];

notInTemplate = [];

headers.forEach(function(obj) {
  if(fields.indexOf(obj) == '-1'){

    console.log(headersObj.c);
    console.log(headersObj.obj);
    console.log(obj);
    notInTemplate.push(obj);
  }
});
console.log(notInTemplate);

I could explain more about my use case, but I just want to be able to "headersObj" property, so I can push it to the "notInTemplate" array. I've distilled it to this fairly simple example. The output of which is:

c undefined c [ 'c' ]

Why is the object property undefined?

You want `headersObj[obj]` instead of `headersObj.obj`. The latter looks for a property named exactly `obj`, and you did not have one. You only have `a`, `b`, and `c`. — Ray Toal, May 11 '18 at 01:24

Mamun · Answer 1 · 2018-05-11T01:28:12.060

You have to use bracket notation ([]) to access the object's property dynamically:

headersObj = {a: "a", b: "b", c: "c"};
headers = ["a", "b", "c"];
fields = ["a", "b"];

notInTemplate = [];

headers.forEach(function(obj) {
  if(fields.indexOf(obj) == '-1'){

    console.log(headersObj.c);
    console.log(headersObj[obj]);
    console.log(obj);
    notInTemplate.push(obj);
  }
});
console.log(notInTemplate);

Undefined object property in foreach loop

1 Answers1