I'm writing a JS code in which I want to delete a specific key from JSON Array and my code is as below.
var obj = [
{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
for (var i = 0; i < obj.length; i++) {
delete obj[i].YYY
}
/*obj=obj.forEach(item =>{ return delete item.YYYY});*/
console.log(obj);This code works fine and is giving me the result as expected, but, When I try to run it using forEach (commented lines), it is showing me undefined.
Where am I going wrong?
Just remove the obj = part of your code. forEach always returns undefined. Since you're modifying the objects in your array and you want to replicate the for loop, forEach is fine, just don't reassign (and no need for return in the callback):
obj.forEach(item => { delete item.YYY; });
Live Example:
var obj = [
{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
obj.forEach(item => { delete item.YYY; });
console.log(obj);(I removed the typo from the forEach code, you had an extra Y.)
That said, there's nothing wrong with a for loop, or you could use a for-of loop:
for (const item of obj
delete item.YYY;
}
Live Example:
var obj = [
{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
for (const item of obj
delete item.YYY;
}
console.log(obj);Another alternative is to create a new array with new objects that don't have the YYY, via map and perhaps with destructuring:
obj = obj.map(({YYY, ...rest}) => rest);
Live Example:
let obj = [
{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
obj = obj.map(({YYY, ...rest}) => rest);
console.log(obj);forEach doesn't return a value.
var obj = [{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
obj.forEach(item => delete item.YYY);
console.log(obj);If you don't want to mutate the original array, you can use Array.map:
var obj = [{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
obj = obj.map(item => (delete item.YYY, item));
console.log(obj);The Return value value of Array.prototype.forEach() is undefined, the actual object is modified. Also, you can shorter your code by removing the curly braces ({...}) and return keyword:
var obj = [
{
XXX: "2",
YYY: "3",
ZZZ: "4"
},
{
XXX: "5",
YYY: "6",
ZZZ: "7"
},
{
XXX: "1",
YYY: "2",
ZZZ: "3"
}
];
obj.forEach(item => delete item.YYY);
console.log(obj);