Javascript Closure and DOM Builder
I am making a DOM builder which I have working succesfully but now I am trying to assign some shorthand functions so that div()
-> e("div")
Here is my code:
//assign these objects to a namespace, defaults to window
(function(parent) {
/**
* Creates string of element
* @param tag The element to add
* @param options An object of attributes to add
* @param child ... n Child elements to nest
* @return HTML string to use with innerHTML
*/
var e = function(tag, options) {
var html = '<'+tag;
var children = Array.prototype.slice.apply(arguments, [(typeof options === "string") ? 1 : 2]);
if(options && typeof options !== "string") {
for(var option in options) {
html += ' '+option+'="'+options[o开发者_如何学JAVAption]+'"';
}
}
html += '>';
for(var child in children) {
html += children[child];
}
html += '</'+tag+'>';
return html;
}
//array of tags as shorthand for e(<tag>) THIS PART NOT WORKING
var tags = "div span strong cite em li ul ol table th tr td input form textarea".split(" "), i=0;
for(; i < tags.length; i++) {
(function(el) { //create closure to keep EL in scope
parent[el] = function() {
var args = Array.prototype.slice.call(arguments);
console.log(args);
args[0] = el; //make the first argument the shorthand tag
return e.apply(e,args);
};
})(tags[i]);
}
//assign e to parent
parent.e = e;
})(window);
What's currently happening is the args array is getting modified each time I call one of the shorthand functions and I assume what needs to happen is a closure somewhere so the args array I created does not get affected each time it is called. Here is the output of the unit tests:
div( div( span("Content")), span()) expected: <div><div><span>Content</span></div><span></span></div>
result: <div><span></span></div>
div( div( span( e("b", e("b", e("b")))), span())) expected: <div><div><span><b><b><b></b></b></b></span><span></span></div></div>
result: <div></div>
Though this doesn't directly answer your question,
for(var el in tags) {
is not entirely correct. tags
is an array, not an object, so its properties cannot be enumerated using for (... in ...)
. Try
for(var el = 0; el < tags.length; el++) {
This can make a huge difference towards the interpreter's understanding of your code... and the correct execution of your algorithm.
Blonde moment, I was overwriting the first element when I meant to use args.unshift(el);
@MvanGeest - doing a for..in
on an array is technically allowed. Arrays are still objects in javascript. The index of the array will be the key if iterated using a for..in
loop. Obviously not the point of using an array in that case, but thought I would clarify.
@Anurag - the forEach
method is not supported in IE8 (not sure about 9) so that might not be a reliable method to use until later on in the future.
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