JavaScript How to change a boolean value in JS? change boolean value java,change boolean value python,change boolean

I'm trying to make a button with two functions:

function bigfont()
{var font_is_small = true
if (font_is_small = true)
{document.getElementById('one').className=
document.getElementById('one').className.replace("font1","font2");
document.getElementById('two').className=
document.getElementById('two').className.replace("font1","font2");
document.getElementById('three').className=
document.getElementById('three').className.replace("font1","font2");
document.getElementById('four').className=
document.getElementById('four').className.replace("font3","font4"); 
font_is_small = true;}
if(font_is_small = false)
{document.getElementById('one').className=
document.getElementById('one').className.replace("font2","font1");
document.getElementById('two').className=
document.getElementById('two').className.replace("font2","font1");
document.getElementById('three').className=
document.getElementById('three').className.replace("font2","font1");
document.getElementById('four').className=
document.getElementById('four').className.replace("font4","font3");
font_is_small = true;}}    

But the variable doesn't change. Could anybody help me?

Answer:1

To change a boolean to its opposite value you can use negation (!), for example x = !x means "set x to false if it's truthy or to true if it's falsy".
If you want the function to toggle between small and big font the simplest way is to place te variable outside of the function:
http://jsfiddle.net/zvoeLu9p/

var font_is_small = true;
function bigfont()
{
    font_is_small = !font_is_small; // switch the boolean
    if (font_is_small){ // no need for == true
        document.body.className=
        document.body.className.replace("font1","font2");
    }
     else { // no need for if condition
        document.body.className=
        document.body.className.replace("font2","font1");
    }
 }    
Answer:2

You have a syntax error:

{var font_is_small = true; //<---- right here you forgot a ;
if (font_is_small == true)//<-- you forgot equal to operators on all if statements

and what is this???!??

document.getElementById('two').className= //<--- blank? the program will be doing this:
document.getElementById('one').className=document.getElementById('one').className.replace("font2","font1");
Answer:3

But you have the variable font_is_small in true all the time you have to change it to false in your code you don't do this.

Answer:4

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