Javascript vs Python variables

Question

I signed up for Codecademy and I am currently in the Javascript path. So, there is this lesson called "Search Text for Your Name" and it consists of writing a multi line string and including your name on it and then write a loop that finds your name and logs it to the console. This is the code:

/*jshint multistr:true */

var text = "Blah Blah Pedro Blah Blah Blah Blah Pedro \
Blah Blah Blah Blah Pedro Blah Blah";

var myName = "Pedro";

var hits = [];

for (var i=0; i < text.length; i++){
    if (text[i] ==="P"){
        for (var j = i; j <(i + myName.length); j++){
            hits.push(text[j]);
        }    
    }
}    

if (hits.length===0){
    console.log("Your name wasn't found!");
}
else {
    console.log(hits);
}

The part that confuses me is the second for loop. When I read "A Byte of Python",it said that when a variable = anothervariable, the variables point to the same place in the memory of the computer. But in the JavaScript code, if I change it, like instead of using hits.push(text[j]) I use hits.push(text[i]) or just switch them in any part of the loop the result is always different. Why is that so? How does Javascript treat this kind of variables?

"When I read "A Byte of Python",it said that when a variable = anothervariable" If that was written there, it is (most likely) wrong. Each variable is usually stored in its own memory location. If you have x = y, then the value of y is copied to the location of x. — Felix Kling
– Felix Kling, Commented Dec 8, 2014 at 20:04
Python = statements are not, technically, "assignments" ... they are bindings. variable = anothervariable is sloppy terminology for Python because of Python's differences, as a late binding dynamically typed language, from most other programming language semantics. "variables" in Python are "names" and "assignment" is binding. The names are both bound to the same object. Javascript's semantics might be entirely different in this regard. That one of the challenges of learning a different language. Semantics matter as well as syntax. — Jim Dennis
– Jim Dennis, Commented Sep 19, 2015 at 23:04

erewok · Accepted Answer · 2014-12-08 19:50:44Z

2

That's a nested for-loop. The outer loop loops over all of the text. When it finds a particular letter, the 'inner' loop kicks off and runs until j gets to this number: i + myName.length.

The whole time that inner loop is running, i is not being incremented.

Think of like this. Imagine you have a (Python style) list of words:

 for someword in some_list:
     for y in someword:
         # This inner loop runs for EVERY x in some_list
         # whatever runs here, runs for the `length` of someword
     # Done with inner loop: back to dealing with outerloop
     # Do something with someword, etc.

The reason that switching hits.push(text[j]) for hits.push(text[i]) results in different hits, is that you are pushing different variables with different values: i, and j.

answered Dec 8, 2014 at 19:50

erewok

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Code Whisperer · Accepted Answer · 2014-12-08 19:46:46Z

1

It takes whatever is stored in 'i' and assigns it to the var 'j'.

More stuff to read about assignment: http://www.w3schools.com/js/js_operators.asp

answered Dec 8, 2014 at 19:46

Code Whisperer

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4 Comments

chilliefiber Over a year ago

Oh, so they are different variables, but with the same information

Code Whisperer Over a year ago

That is correct. They will have the same information just because of the assignment. As soon as one is assigned a different value they will have different information in them while still being different variables.

chilliefiber Over a year ago

Thanks. It's different than Python

Code Whisperer Over a year ago

Yes it is. Between languages there will be more differences as well. If or when you work in C or JAVA it will get more confusing because both outcomes are possible there. Especially in C.

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