Training JS #10: loop statement --for

Description:

The for loop is a very frequently used loop in JS.

Recall in lesson 9 we wrote a while loop:

function sum1_100(){
  let sum=0,num=1
  while (num<=100){
    sum+=num;
    num++;
  }
  return sum;
}

We can rewrite it using a for loop, like this:

function sum1_100(){
  for (let sum=0,num=1;num<=100;num++){
    sum+=num;
  }
  return sum;
}

As you see, there are three parts in the parentheses, separated by ";". The first part, var sum=0,num=1, is the initialization. This part will run before the loop starts. The second part, num<=100 is the conditional expression. The conditional expression is checked before the start of each time through the loop. When the value of the expression is false, the loop will be terminated. The third part, num++ will run after the code block, and is usually used for increasing and decreasing variables.

For the example above, the running order of the code is:

                              <--- back to part 2
                  -------------------------------------------
                  |                 true                    |
let sum=0,num=1  --->  num<=100 ?  ------> code block---> num++
                                |  
                           false|
                       loop terminated

When you need to traverse an array, you can use the for loop to access each element using its index. Here's an example:

function displayElements(array){
  for (let i=0;i<array.length;i++){
    console.log(array[i]);
  }
}

This function will display every element of the array on your screen.

Ok, lesson is over, let's do a task with for.

Task

The function pickIt accepts 1 parameter, arr, which is an array of numbers. We need to traverse arr by using a for loop. If an element is an odd number, push it to the odd array, and if it's an even number, push it to the evenarray.

I've defined two arrays odd and even in the function, and also wrote the return statement. Your work is to write a for loop.

If you forgot how to push an element to an array, please refer to lesson 4.

Series

Fundamentals

Tutorials

Similar Kata:

More By Author:

Check out these other kata created by myjinxin2015

Stats:

Created	Apr 28, 2016
Published	Apr 28, 2016
Warriors Trained	20086
Total Skips	756
Total Code Submissions	34045
Total Times Completed	15434
JavaScript Completions	15435
Total Stars	190

% of votes with a positive feedback rating	94% of 2094
Total "Very Satisfied" Votes	1892
Total "Somewhat Satisfied" Votes	172
Total "Not Satisfied" Votes	30

Kata