I know that I can import an css file in other css file with @import
Ex: @import "style.css"; and i use this in allcss.css

Can I do something like this in javascript, import a javascript in other javascript ;

Try this:

<script type="text/javascript">
function importScript(url){
    var tag = document.createElement("script");
    tag.type="text/javascript";
    tag.src = url;
    document.body.appendChild(tag);
}
window.onload = function(){
    // imports go here
    importScript("foo.js"); // example
};
</script>

I am actually looking for a way to do this in JS, just like in php : include("filename");

I am doing this because i want to reduce http requests, bcause i have to load a few js scripts. is it good to do this?

I am doing this because i want to reduce http requests

The only way to do that in js is by merging all the files in 1.
Javascript being a client side language, including it from another javascript will still make 1 request to your server.
The source has to be read.

Ya, i got that,

Thanks tripy!