CODEWITHSUNDEEP
javascript
Matt Hintzke
Matt Hintzke

Reputation: 7984

Javascript basic execution order

I know PHP, server-side scripts, run first and output the html to the browser, then javascript is executed. However, I am trying to get a feel for how the javascript is executed and can't quite figure it out.

Is Javascript executed top-down and is consistent with this top-down execution? I am dynamically creating javascript in PHP which is triggered by events in my webpage's original javascript.

Will created JS execute exactly where I put it or will it fire before? after?

Thanks

Upvotes: 1

Views: 278

Answers (4)

pozs
pozs

Reputation: 36214

Is Javascript executed top-down and is consistent with this top-down execution?

Yes

With a lesser-known exception:

Function statements will be executed before any other statements (but not function operators).

So this would run fine:

f();

function f() { console.log("a"); }

Upvotes: 0

swapnilsarwe
swapnilsarwe

Reputation: 1300

Well javascript will execute one line after the another. But also javascript is the event based language hence there will be certain part of the code which will be based on events and will execute only when the events take place.

For eg: click,hover etc events

or functions like setTimeout and setInterval

these function will execute only when the particular events takes place

Upvotes: 2

Conner
Conner

Reputation: 31040

Javascript is read and run by the user's web browser whereas PHP is run server-side. The PHP code is compiled, HTML (with Javascript) is served, the user's browser reads the HTML and Javascript.

Upvotes: 0

Alex
Alex

Reputation: 35399

JavaScript is executed by the clients browser and is parsed in conjunction with the HTML and CSS, whichever comes first.

Is Javascript executed top-down and is consistent with this top-down execution?

Yes

Will created JS execute exactly where I put it or will it fire before? after?

JavaScript inserted into the DOM will be parsed/executed immediately.

Upvotes: 1

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