var text="";

[Fangorn]

Hi,

 

I just started to study javascript and I came across in one of your page to the following notation:

 

var text="";

 

The page is from w3school tutorial: http://www.w3schools.com/js/tryit.asp?filename=tryjs_loop_for_ex

 

I do not understand what it means and why should be used in the loop of the above example.

I tried to define var text; in its place but the result is:

 

undefinedThe number is 0The number is 1The number is 2The number is 3The number is 4

 

The only difference is the world 'undefined' at the beginning of the first line.

 

Many thanks in advance for your help

[niche]

It defines the variable called text as a string.

 

It's a to "get the variable on the page" so to speak.

 

It is simply a way to initialize a variable.

[Fangorn]

Thanks niche,

 

so I suppose is always fundamental to define a variable as a string or as a number (var number = 0 or var text="").

 

I still have to understand how the loop works and the importance of the variable 'text' for the code itself.

I tried to delete the '+' from the code, and use text = ... instead of: text += "The number is " + i + "<br>";

and the result is only the last line, 'The number is 4'.

 

So I do not understand what text = text + "The number is " + i + "<br>"; means inside the loop, if one should explain it in words.

Taken for granted that understand "The number is " + i + "<br>", I suppose is just the code text = text + ... that prints out all the results of the loop. What happens there?

 

For instance, for i=0 we should have: text = text + The number is 0...

So what does 'text' represent?

 

I am sorry if the question looks so banal, but I am really stuck in this loop

Edited July 16, 2014 by Fangorn

[davej]

function myFunction() {    var text = ""; // declare the var and initialize the var to an empty string    var i; // declare the var    for (i = 0 ; i < 5 ; i++) {// loop from i=0 to i=4        text += "The number is " + i + "<br>"; // append a string to the string ending with a newline    }    document.getElementById("demo").innerHTML = text;// print the string to the screen inside the demo block}

[Ingolme]

text is a string.

 

When you do +=, or text = text + "string", what you're doing is making text have the same value it did before, but with something extra added onto it.

 

text = "A" means that text will become "A".

text += "A" means that text will become the current value of text followed by "A".

 

In the loop, if you use text = "The number is " + i + "<br>" then text will keep changing its value and will end up having the last value it was given. All a loop does is run the same code again multiple times.

[Fangorn]

Got it!!!

 

Therefore, using the code above, it will be:

for i = 0: text = "The number is 0" + <br>

for i = 1: text = text + "The number is 1" that is: text = "The number is 0" + <br> + "The number is 1" + <br>

for i = 2: text = text + "The number is 2" that is: text ="The number is 0" + <br> + "The number is 1" + <br> + "the number is 2" + <br>

... etc ...

 

Thank you very much!!! :)