I am saving some data in order using array
s, and I want to add a function that the user can reverse the list. I can't think of any possible method, so if anybody knows how, please help.
Steps to reverse an array without using another array in C:Set i=0 to point to the first element and j=length-1 to point to the last element of the array. Run while loop with the condition i<j . Inside loop swap ith and jth element in the array. Increment i and decrement j .
Javascript has a reverse()
method that you can call in an array
var a = [3,5,7,8]; a.reverse(); // 8 7 5 3
Not sure if that's what you mean by 'libraries you can't use', I'm guessing something to do with practice. If that's the case, you can implement your own version of .reverse()
function reverseArr(input) { var ret = new Array; for(var i = input.length-1; i >= 0; i--) { ret.push(input[i]); } return ret; } var a = [3,5,7,8] var b = reverseArr(a);
Do note that the built-in .reverse()
method operates on the original array, thus you don't need to reassign a
.
Array.prototype.reverse()
is all you need to do this work. See compatibility table.
var myArray = [20, 40, 80, 100]; var revMyArr = [].concat(myArray).reverse(); console.log(revMyArr); // [100, 80, 40, 20]
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