如何使用JavaScript从数组中删除\\'a \\'等值

Question

I am stuck at this challenge on codewars where I have to return only numbers from an array as a new array and neglect all non-numbers.

I was presented with something like this ['1', '2', \\'a\\', \\'b\\']. This is meant it return just [1, 2]

I tried this.

function filter_list(l) {
    return l.filter(c => c>=0 && c <= 999)
} 

I got my [1, 2] in the case of this ['1', '2', \\'a\\', \\'b\\'] but got a [\\'1\\'] in the case of [\\'1\\'] instead of []

What do I do?

Answer 1

You need to check if the elements are actually numbers or if they are strings containing numbers. Here are a couple of solutions using filter:

function num (arr) {
  return arr.filter(c => Number.isInteger(c));
}

function num2 (arr) {
  return arr.filter(c => typeof c === 'number');
}

Check out these resources:

Number.isInteger()- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger

typeof- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof

Answer 2

this should work ( if you pass an array without the backslashes like [1,'2','a'] )

function filter_list(l) {
    return l.filter(c => parseInt(c) >=0 && parseInt(c) <= 999)
}