Javascript - Prompt for values (and add values to array) until user inputs a specific value

Question

Ladies and gentlemen,

I'm stuck. I've been pondering this (and obviously have failed since I'm asking for your valuable assistance) in trying to get my code to work.

I need to come up with a simple (...I'm sorry, i'm new to this) code that prompt users to keep entering names using a loop. If the user does not enter 'q'(without quotes) and if the value entered is NOT null, then the value entered should be added to the array (in my case, names).

If the user enters 'q', the loop should stop, 'q' will not be entered in the array and the list of names should be printed (through the second function in my code).

Here's what I have so far... I can make the code work if I tell the loop to run i<5... it runs 5 times and then it stops. But it fails if i do i < names.length..it causes it say that length is null or not an object (on line 10). That's problem one. And for the life of me, I can't figure out how to add the logic that will run the loop until user enters q.

Please help!

Thank you.

function getNames(){
var names = new Array();
    for(i=0;i<names.length;i++){ /*if i do i=0;i<5;i++, the code works; it doesn't with this*/
    names[i] = prompt("Enter an item to add to the Name list (enter \'q\' to quit","");
}
printNames(names);
}

function printNames(names) {
for(x=0; x < names.length;x++){
document.write(names[x] + '<br />');
}

}
getNames();
printNames();

epascarello · Accepted Answer · 2012-12-24 16:20:29Z

2

I am sure somewhere in your class/book it talks about while loops. So you want to use a while loop if you want them to keep entering without a limit.

while (myCondition===true) {
  //do something
}

Now look at your for loop and figure out why it is failing.

for(i=0;i<names.length;i++)

Look at what it is doing:

i = 0
names.length = 0

Is 0 < 0?

edited Dec 24, 2012 at 16:20

answered Dec 24, 2012 at 16:08

epascarello

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5 Comments

Guanaco_Sensei Over a year ago

Fair enough. But have you any input on why my code above fails to run when i enter use i < names.length but not when i say i < 5? I need it to run as long as there is at least one item in the array.

epascarello Over a year ago

Edited it to answer your question from the comment.

Moritz Roessler Over a year ago

+1 for letting the OP being able to learn by finding the "Answer" by himself =)

Guanaco_Sensei Over a year ago

Oh duh! I printed it out and it was easier to see.. for some reason. SO i changed that to i >= names.length and that ran the code perfect. I was able to figure out the while condition, too. Thank you for the enlightenment!

Guanaco_Sensei Over a year ago

Update, to improve it, I used a DO WHILE loop and that worked fantastically well. Within the DO WHILE I created an IF statement that adds value to array only if the input has a value (so > than '' ).

Xaxis · Accepted Answer · 2012-12-24 16:15:14Z

0

Well to start with Problem 1:

Your names array begins with a length property of 0 and so your first for loop doesn't run because 0 is not less than 0.

Which leads to Problem 2:

Again since nothing was entered into your names array your second for loop again does nothing and doesn't execute document.write because the length property of your array is still 0.

answered Dec 24, 2012 at 16:15

Xaxis

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