For loop array issues with javascript and jquery

Question

var link = [];

for(var x = 0; x < id_ion['ions'].length; x++) {
    var source,
    target;

    if(id_ion['ions'][x]['ID1'] == data.main[0].ID1) {
        source = id_ion['ions'][x]['ID1'];
        target = id_ion['ions'][x]['ID2'];
    } else {
        source = id_ion['ions'][x]['ID2'];
        target = id_ion['ions'][x]['ID1'];
    }
    var_edges.push({data:{
            source: source,      
            target: target,
            exp: id_ion['ions'][x]['exp'],
            pub: id_ion['ions'][x]['pub'],
            name: id_ion['ions'][x]['name'],
            age: id_ion['ions'][x]['age']
    }});

Hello, I am a beginner and I am trying hard to understand coding. I have looked everywhere and I was not able to understand this code completely.

what is the problem? what is it that you don't understand? don't post too broad questions... — Tommaso Bertoni
– Tommaso Bertoni, Commented Mar 15, 2016 at 15:06
I know there's an array but I can't understand the logic of the other variables and their functions. — albertgeorge253
– albertgeorge253, Commented Mar 15, 2016 at 15:09
If you don't understand the basic javascript syntax, you should take a general course in the language (or read a book, study online etc.) before being expected to work on existing code. — user162097
– user162097, Commented Mar 15, 2016 at 15:17
also you should know that in Javascript x['y'] is the same as x.y (assuming y is a word, not something that can't be a variable). So id_ion['ions'][x]['age] is the same as id_ion.ions[x].age — Siderite Zackwehdex
– Siderite Zackwehdex, Commented Mar 15, 2016 at 15:21

Zach L · Accepted Answer · 2016-03-15 18:09:58Z

3

This is pretty basic code, so you should look into some basic online tools to boost your understanding. codecademy teaches basic javascript and would be a good spring board. I'll try to cover each chunk of code with the basics.

for(var x = 0; x < id_ion['ions'].length; x++) {

This is a for loop. Its going to iterate through each element of the array id_ion['ions'] so that you can evaluate them one by one. Each time the for loop goes through an iteration, x increments. So the first time we look at id_ion['ions'][0] which is the first element, next we look at id_ion['ions'][1] and so on.

    if(id_ion['ions'][x]['ID1'] == data.main[0].ID1) {
        source = id_ion['ions'][x]['ID1'];
        target = id_ion['ions'][x]['ID2'];
    } else {
        source = id_ion['ions'][x]['ID2'];
        target = id_ion['ions'][x]['ID1'];
    }

This is an if/else block. In this conditional, we see if the element that our for loop is currently evaluating is equal to data.main[0].ID1. If it is, we set the source and target one way, if not, we run the else and set them the other way.

    var_edges.push({data:{
            source: source,      
            target: target,
            exp: id_ion['ions'][x]['exp'],
            pub: id_ion['ions'][x]['pub'],
            name: id_ion['ions'][x]['name'],
            age: id_ion['ions'][x]['age']
    }});

This creates an array called 'data' which you fill with data that you collect for each iteration of your loop and pushes it into another array called var_edges. Do a little research and ask around for some good books/tutorials that can help you learn. You'll start to understand javascript in no time.

edited Mar 15, 2016 at 18:09

answered Mar 15, 2016 at 15:45

Zach L

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4 Comments

albertgeorge253 Over a year ago

Thank you a lot Zach L for your answer and valuable time. It is much clearer for me now.

Zach L Over a year ago

No problem. When you're learning, you're going to get confused or stuck. Search stackoverflow and generally, someone has already had the same issue and gotten a solution that can help you figure out your error. Happy Coding. :)

albertgeorge253 Over a year ago

Thanks again for the advice.

Zach L Over a year ago

If you feel like this answered your question, feel free to accept it as the correct answer

ahbon · Accepted Answer · 2016-03-15 15:13:38Z

0

 for(var x = 0; x < id_ion['ions'].length; x++) {}

is used to deal with all the elements of the table.

var source, target;
if(id_ion['ions'][x]['ID1'] == data.main[0].ID1) {
   source = id_ion['ions'][x]['ID1'];
   target = id_ion['ions'][x]['ID2'];
} else {
   source = id_ion['ions'][x]['ID2'];
   target = id_ion['ions'][x]['ID1'];
}

is used to put the table elements into variables with an if statement.

var_edges.push({data:{
   source: source,      
   target: target,
   exp: id_ion['ions'][x]['exp'],
   pub: id_ion['ions'][x]['pub'],
   name: id_ion['ions'][x]['name'],
   age: id_ion['ions'][x]['age']
}});

is used to create an other array thanks to the push function.

answered Mar 15, 2016 at 15:13

ahbon

5115 silver badges21 bronze badges

1 Comment

albertgeorge253 Over a year ago

Thank you a lot @ahbon for your answer and valuable time. It is getting clearer for me to understand now

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