javascript - How to filter elements returned by QuerySelectorAll -

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i'm working on javascript libarary, , use function match elements:

$ = function (a) {     var x;     if (typeof !== "string" || typeof === "undefined"){ return a;}      //pick quickest method each kind of selector     if(a.match(/^#([\w\-]+$)/))     {         return document.getelementbyid(a.split('#')[1]);     }     else if(a.match(/^([\w\-]+)$/))     {         x = document.getelementsbytagname(a);     }     else     {         x = document.queryselectorall(a);     }      //return single object if applicable     return (x.length === 1) ? x[0] : x; };

there occasions want filter result of function, pick out div span, or #id div or other simple selector.

how can filter these results? can create document fragement, , use queryselectorall method on fragment, or have resort manual string manipulation?

i care modern browsers, , ie8+.

if want @ rest of library, it's here: https://github.com/timw4mail/kis-js

edit:

to clarify, want able $_(selector).children(other_selector) , return children elements matching selector.

edit:

so here's potential solution simplest selectors: 

tag_reg = /^([\w\-]+)$/; id_reg = /#([\w\-]+$)/; class_reg = /\.([\w\-]+)$/;  function _sel_filter(filter, curr_sel) {     var i,         len = curr_sel.length,         matches = [];      if(typeof filter !== "string")     {         return filter;     }      //filter tag     if(filter.match(tag_reg))     {         for(i=0;i<len;i++)         {             if(curr_sell[i].tagname.tolowercase() == filter.tolowercase())             {                 matches.push(curr_sel[i]);             }         }     }     else if(filter.match(class_reg))     {         for(i=0;i<len;i++)         {             if(curr_sel[i].classlist.contains(filter))             {                 matches.push(curr_sel[i]);             }         }     }     else if(filter.match(id_reg))     {         return document.getelementbyid(filter);     }     else     {         console.log(filter+" not valid filter");     }      return (matches.length === 1) ? matches[0] : matches;  }

it takes tag div, id, or class selector, , returns matching elements curr_sel argument.

i don't want have resort full selector engine, there better way?

i don't think question right. why want "filter" result of queryselectorall() infact, kind of filter itself. if query div span or better #id div, results filtered, no ?

however, can apply array.prototype.filter static result of queryselectorall follows:

var filter   = array.prototype.filter,     result   = document.queryselectorall('div'),     filtered = filter.call( result, function( node ) {         return !!node.queryselectorall('span').length;     });

that code first use queryselectorall() query <div> nodes within document. afterwards it'll filter <div> nodes contain @ least 1 <span>. code doesn't make sense , demonstrative purposes (just in case member wants create donk comment)

update

you can filter element.comparedocumentposition. i'll tell if elements disconnected, following, preceding, or contained. see mdc .comparedocumentposition()


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