I have that code:
arr = arr.sort(function (a, b) {
return a.time>b.time
})
Do I need to redefine arr or it is possible just to call sort function? like this:
arr.sort(function (a, b) {
return a.time>b.time
})
Will the sort and filter functions change the original array?
Use slice() to sort a copy of the original array.
var arr =[{time:4},{time:3},{time:6}];
arr.sort(function (a, b) {
return a.time-b.time;
});
will mutate the original array and returns :
[ { time: 3 }, { time: 4 }, { time: 6 } ]
and console.log(arr) returns
[ { time: 3 }, { time: 4 }, { time: 6 } ]
but
var arr =[{time:4},{time:3},{time:6}];
arr.slice().sort(function (a, b) {
return a.time-b.time;
});
returns
[ { time: 3 }, { time: 4 }, { time: 6 } ]
but will not affect the original array.
console.log(arr) returns
[ { time: 4 }, { time: 3 }, { time: 6 } ]
It's a decent question, and let's answer it properly:
const a = [1, 2, 3];
const b = a.sort();
console.log(a === b); // true
there is your answer. The === operator for objects will compare memory locations, so it's the same object in memory.
Which is a shame because it would be better if sort created a new array (immutability etc), but in many languages it does not return a new array, but the same array (reordered).
So if you want it to be immutable, you can do:
const a = [1, 2, 3];
const b = a.slice(0).sort();
arr.push(4,5,6) didn't mutate the original. That would be a nightmare. You'd have to rely solely on arr = arr.concat([4,5,6]), and you still couldn't update references.It sorts the array in place (modifying the array). From MDN:
The sort() method sorts the elements of an array in place and returns the array. The sort is not necessarily stable. The default sort order is according to string Unicode code points.
Yes it modifies the original array.
const a = [1, 2, 3];
const b = a.sort();
const c = [...a].sort(); //es6 feauture similar to slice(0)
console.log(a === b); // true
console.log(a === c);//false
Or from ES6:
const a = [1, 2, 3];
const b = [...a].sort();
Will the sort and filter functions change the original array
For sort() method, Answer is Yes but for filter() method answer is No.
Let me explain with an example :
// Original Array
const arr = [5, 4, 3, 2, 1];
// Sorting array values and assigned in a variable.
const sortedArr = arr.sort((a, b) => a-b);
// Original array modified.
console.log(arr); // [1,2,3,4,5]
// New variable with sorted array.
console.log(sortedArr); // [1,2,3,4,5]To prevent the original array to get modified, We can use to[Operation] that return a new collection with the operation applied (This is currently at stage 3, will be available soon).
const arr = [5, 4, 3, 2, 1];
const sortedArr = arr.toSort((a, b) => a-b);
console.log(arr); // [5, 4, 3, 2, 1]
console.log(sortedArr); // [1, 2, 3, 4, 5]
sortchanges the array. But the comparator function will work based on the return value of (+n, 0, -n) notboolean. Please change the comparator.