Question 190196 in Javascript Question posted in
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Javascript efficient way of checking object attribute and assigning

I have a Javascript object otherObj and I construct myObj dynamically based on non-undefined values of otherObj. As of now, I manually compare and assign as below. But was wondering if there can be a more efficient way…Also not sure if it is possible to make it even more dynamic i.e. say if attr3 gets added in future, that also gets considered automatically.

let myObj = {};
if (otherObj.attr1 !== undefined) {
    myObj['attr1'] = otherObj.attr1;
}
if (otherObj.attr2 !== undefined) {
    myObj['attr2'] = otherObj.attr2;
}
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2

Answers


  1. 0

    You can try using for…in to iterate over the properties of otherObj and conditionally assign them to myObj:

    let myObj = {};

for (let prop in otherObj) {
  if (otherObj[prop] !== undefined) {
    myObj[prop] = otherObj[prop];
  }
}
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  2. 0

    You can use the Nullish coalescing operator

    ["attr1","attr2"].forEach(attr = myObj[attr] = otherObj[attr] ?? "";

    Be careful if the otherObj[attr] is an object. You will need to clone it if you do not want subsequent actions on myObj to affect otherObj

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