如何使用 Lodash 以相反的顺序迭代数组？

Question

I want to iterate over an array in reverse order using Lodash. Is that possible?

My code looks like below.

var array = [1, 2, 3, 4, 5];
_.each(array, function(i) {
   _.remove(array, i);
});

When I do _.pullAt(array, 0) new array is [2, 3, 4, 5] . All array elements shifted to left by 1 position, and current index is pointing to element 3. After next iteration, 3 will get deleted and then 5. After 3rd iteration array contains [2, 4] which I couldn't delete.

If I iterate over the array in reverse order, then this problem won't arise. In Lodash, can I iterate over an array in reverse order?

Answer 1

You can use _.reverse available in version 4:

var array = [1, 2, 3, 4, 5];
array = _.reverse(array)
console.log(array)
//5, 4, 3, 2, 1

Answer 2

See How do I empty an array in JavaScript? if you only want that and choose your weapon .

Otherwise, strictly answering the question, to iterate the indices from the length of the array to zero, you could use the "down-to" --> operator ¹ . But that's not really necessary, even underscore isn't necessary in this case as the .pop function is enough.

 var arr = [1, 2, 3, 4, 5], index = arr.length; while (index --> 0) { console.log(index); arr.pop(); } console.log(arr);

If you're using Lodash like the functions referenced in the question seem to indicate, you could use _.eachRight .

 var arr = [1, 2, 3, 4, 5]; _.eachRight(arr, function(value) { console.log(value); arr.pop(); }); console.log(arr);

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script>

---

^{1 The down-to operator doesn't exist and is only a -- decrement followed by a > comparison.}