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I am trying to understand how the sort() function works along with the callback function passed into it. More specifically the values of a and b
Example code:
var n = [4, 11, 2, 10, 3, 1];
n.sort(function(a, b) {
console.log(a);
console.log(b);
console.log('--')
return a-b;
});
Result:
4
11
--
11
2
--
4
2
--
11
10
--
4
10
--
11
3
--
10
3
--
4
3
--
2
3
--
11
1
--
10
1
--
4
1
--
3
1
--
2
1
--
The first round I can follow that a = 4, and b = 11, easy to follow.
The second round I can follow that a = 11 and b = 2.
But after that I sort of loose track of what actually is going, for example when you get to when a = 4 and b = 3. How is this actually working? I tried working it out on paper but could not see the logic in the output of a and b.
582
The function(a,b) that we provide simply compares two items and returns a negative number if a is “smaller” than b according to our sort criteria, or a positive number if a is “larger” (i.e. should be sorted after b ), or 0 if the order of a and b in the Array should not be changed.
The sort() method sorts the elements of an array in place and returns the reference to the same array, now sorted. The default sort order is ascending, built upon converting the elements into strings, then comparing their sequences of UTF-16 code units values.
Passing a function to another function or passing a function inside another function is known as a Callback Function. Syntax: function geekOne(z) { alert(z); } function geekTwo(a, callback) { callback(a); } prevfn(2, newfn); Above is an example of a callback variable in JavaScript function.
Use the sort method in the nonMutatingSort function to sort the elements of an array in ascending order. The function should return a new array, and not mutate the globalArray variable.
Looks like a modified bubble sort. You can see what is happening when you compare the state of the array at each step - I have added them below.
Move the value from index 1 as low as it should go. (index 0-1 are in order) Now move the value from index 2 as low as it should go. (index 0-2 are in order) Now move the value from index 3 as low as it should go. (index 0-3 are in order)
Since we know how much of the array is in order we short circuit the comparisons and jump to the next index as soon as the comparison function is not negative.
4
11
-- [4, 11, 2, 10, 3, 1];
11
2
-- [4, 2, 11, 10, 3, 1];
4
2
-- [2, 4, 11, 10, 3, 1];
11
10
-- [2, 4, 10, 11, 3, 1];
4
10
-- [2, 4, 10, 11, 3, 1];
11
3
-- [2, 4, 10, 3, 11, 1];
10
3
-- [2, 4, 3, 10, 11, 1];
4
3
-- [2, 3, 4, 10, 11, 1];
2
3
-- [2, 3, 4, 10, 11, 1];
11
1
-- [2, 3, 4, 10, 1, 11];
10
1
-- [2, 3, 4, 1, 10, 11];
4
1
-- [2, 3, 1, 4, 10, 11];
3
1
-- [2, 1, 3, 4, 10, 11];
2
1
-- [1, 2, 3, 4, 10, 11];
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