Thoughts arising from JavaScript array loops

Look at the code and don't speak:

Copy the codeThe code is as follows:

 
var i=; 
while(i--) 
{ 
//What should I write?
} 

The above is GoogleIn the programRecommended improvementscode. Think about why i-- When i is 0, the while loop ends?

The following code is equivalent to it:

Copy the codeThe code is as follows:

 
var i=; 
for(;i--;) 
{ 
//i--Written in the middle of two semicolons, is it strange?  Isn't it strange?
} 

Shocked? Don't feel it?

Well. What do we usually write between two semicolons? This i--according to common sense, it should be after the second semicolon. Let's take a look at the C language code:

Copy the codeThe code is as follows:

 
int main() 
{ 
int i = 5; 
while(i--) 
{ 
printf("%d ", i); 
} 
while(1); 
return 0; 
} 

The results of the run are also surprisingly consistent with JavaScript!

All right. I don't know why this is? Only know that the value 0 is converted to a boolean value to false:

var i= !!0;

The other values are converted to Boolean values to true. The example program code above is an explicit conversion of numeric values to boolean values.

If 0 is implicitly converted to false, use the following JS program to test:

Copy the codeThe code is as follows:

 
var i=0; 
if(i) 
{ 
alert('if'); 
} 
else{ 
alert('else'); 
} 
alert('No matter how if and else program, you have to go here');

If this sample code is not "practical" at all? Well, here is a code sample snippet of a Tudou.com front-end development expert:

Copy the codeThe code is as follows:

 
var obj = {status:0, msg:'xxxx'}; 
var data =  || 'xxxx'; 

This is always "hidden" enough!

I would like to emphasize again: the condition that the implicit conversion of the numeric value 0 to the Boolean value false is a conditional expression determined by Boolean in if(), while(), and the middle of the two semicolons such as for(;;).