Question

Today I came across the following JS:

    for (var b = k, d = function (c) {
       // function body
    }, a = b.p, e = z; 0 < c;) {

    } // for loop closing cause

Can some please explain what’s happening here? I’m confused about the function, normal “for” loop would do:

    for(x=0; x<something; x++){

    }

This loops appears to follow a different structure:

    for(x=0; d = function(c), a = somevar, e = somevar, 0 < c)

Why are there 5 elements in the for loop? Thanks!

Answer 1

Ill explain, but basically this is not good code.

Its not good code because you need to go online just to figure it out.

for (var b = k, d = function (c) {
// function body
}, a = b.p, e = z; 0 < c;) {

} // for loop closing cause

is the equivalent of

var b = k,
    d = function (c) {
      // function body
    },
    a = b.p,
    e = z;

for (; 0 < c; ){

}

for loop parents has three parts
1. Initialization
2. Condition
3. Ending statement

That must all be separated by a ;

except these are all optional in a for loop

for (var init = 0; init < 10; init += 1) {}

same as:

var init = 0;
for (;;) {
 if (!(init < 10)) {
  break;
 }
 init += 10;
}