CODEWITHSUNDEEP
javascriptgoogle-chrome-extension
user1261718
user1261718

Reputation: 37

How to keep global variable unchanged in js

It's a Chrome Extension JS, i want to compare the DOM tree structure between DOM loaded and all these files loaded.Here I declare two variable first and then it will run into these 2 Listeners. But txt1 won't keep the value in the 1st listener, no matter declare it with var or window. So how can I keep the global value? Or can I bypass it in other ways? 

    function tw1(){ 
    var treeWalker = document.createTreeWalker(document,NodeFilter.SHOW_ELEMENT,{ acceptNode: function(node) { return NodeFilter.FILTER_ACCEPT; } },false);

    var ar = new Array();
    var count=0;
    while(treeWalker.nextNode()) {
    ar[count]=treeWalker.currentNode.nodeName;
    count++;
    console.log(treeWalker.currentNode.nodeName);

    }

    var txt="";
    for (var i=0;i<count;i++)
    {
    txt=txt+ar[i]+i+"\t";
    }
    //console.log(txt); 
    return txt; 

    }

    function compare(str,str0)
        { 
         if(str.indexOf(str0) == 0&& str0.indexOf(str) == 0)
         {
          return 0;
         }
         else
         {
          return 1;
         }
    }

    window.txt1="";
    window.txt2="";

    document.addEventListener('DOMContentLoaded', function() {
        window.txt1=tw1();

    }, false);

    window.addEventListener('load', function() {
        window.txt2=tw1();
        console.log(window.txt1);
        console.log(window.txt2);
        if(compare(window.txt1,window.txt2)!=0)
            alert("This page is possibly malicious.");

    }, false);

Upvotes: 0

Views: 391

Answers (1)

Sushanth --
Sushanth --

Reputation: 55750

Simplest is adding a check condition 

if(!window.txt1.length)
    window.txt1=tw1();

Upvotes: 1

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