While Loops Syntax Errors

Question

The course is asking me to form a while loop and I keep getting errors or infinite loops. What am I doing wrong?

var understand = true;

while(understand= true){
    console.log("I'm learning while loops!");
    understand = false;
}

I'm curious, why did you think that = would behave differently in different locations? I recommend to read the MDN JavaScript Guide to learn the basics: developer.mozilla.org/en-US/docs/Web/JavaScript/Guide — Felix Kling
– Felix Kling, Commented Aug 20, 2014 at 22:34
I'm using Codeacademy to learn Javascript and it never mentioned that = and == are used differently. I just assumed they were interchangeable. — Tim
– Tim, Commented Aug 20, 2014 at 22:39

Timeout · Accepted Answer · 2014-08-20 22:50:34Z

4

You are using an assignment operator (=) and not an equals test (==).

Use: while(understand == true)

Or simplified: while(understand)

Update from comments:

=== means the value and the data type must be equal while == will attempt to convert them to the same type before comparison.

For example:

"3" == 3 // True (implicitly)
"3" === 3 // False because a string is not a number.

edited Aug 20, 2014 at 22:50

answered Aug 20, 2014 at 22:30

Timeout

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4 Comments

Tim Over a year ago

Thank you very much. That fixed it and helped me clear up the difference between those two.

Tim Over a year ago

Also, can you explain to me what === is? Is it any different?

Spencer Wieczorek Over a year ago

@Tim === is strict comparison. While == will attempt to make both sides the same data type, === will not. so 1 == "1" works while 1 === "1" does not.

Felix Kling Over a year ago

@SpencerWieczorek: I assume "make both sides the same" means "converting both values to the same data type".

Spencer Wieczorek · Accepted Answer · 2014-08-20 22:41:57Z

3

= means assignment, while == is comparison. So:

while(understand == true)

Also note that while and other branch structures, take conditions. Since this is a Boolean you can just use itself:

while(understand)

Also a note of the difference between == and === (strict comparison). The comparison == will attempt convert the two sides to the same data type before it compares the values. While strict comparison === does not, making it faster in most cases. So for example:

1 ==  "1"  // This is true
1 === "1" // This is false

edited Aug 20, 2014 at 22:41

answered Aug 20, 2014 at 22:30

Spencer Wieczorek

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