Higher Order Function Javascripts

I'm trying to understand better and start coding JS with higher order functions. Below is just a practice I'm doing, and I want to output an array of numbers * 2. function each(col

Solution 1:

I think this will work for you:

// Let's call this what it is
function getNumbersFromArray(collection, callback) {
    var arr = [],
        i = 0;

    for (; i < collection.length; i++) {
        // Check if isNumber and do mutliplication here
        if (callback(collection[i])) {
            arr.push(item * 2);
        }
    }

    return arr;
}

// Make isNumber actually return a boolean
function isNumber(item) {
    return typeof item === "number";
}

// call console.log()
console.log(getNumbersFromArray([1, 2, 3, 4, "String"], isNumber)); 

Solution 2:

no output is showing because neither of your functions return anything.

here, i'd have your callback just apply the multiplication and return that value, then push to an array in your each function

function each(collection, callback) {
  var arr = [];
  for(var i = 0; i < collection.length; i++) {
      var result = callback(collection[i])
      if (typeof result !== 'undefined') {
        arr.push(callback(collection[i]));
      }
    }
  return arr
}

function isNumber(item) {
    if (typeof item === "number") {
      return item * 2;
    }
}