js converts array-like objects into array objects_javascript skills

In standard browsers, it seems that as long as the object has a length property, it can be converted into an array, but this is not the case in IE.

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Then let’s take a look at the major Class library processing:

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The code is as follows:

//jQuery’s makeArray
var makeArray = function( array ) {
var ret = [];
if( array != null ){
var i = array.length;
// The window, strings (and functions) also have 'length'
if( i == null || typeof array === "string" || jQuery.isFunction(array) || array.setInterval )
ret[0] = array;
else
while( i )
ret[--i] = array[i];
}
return ret;
}

jQuery The object is used to store and process DOM elements. It mainly relies on the setArray method to set and maintain the length and index. The parameter of setArray is required to be an array, so the status of makeArray is very important. This method is guaranteed to return an empty array even if there are no parameters.
$A method of Prototype.js

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The code is as follows:

function $ A(iterable) {
if (!iterable) return [];
if (iterable.toArray) return iterable.toArray();
var length = iterable.length || 0, results = new Array (length);
while (length--) results[length] = iterable[length];
return results;
}

mootools’ $A method

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The code is as follows:

function $A(iterable){
if (iterable.item ){
var l = iterable.length, array = new Array(l);
while (l--) array[l] = iterable[l];
return array;
}
return Array.prototype.slice.call(iterable);
};

Ext’s toArray method

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The code is as follows:

var toArray = function(){
return isIE ?
function(a, i, j, res){
res = [];
Ext.each(a, function(v) {
res.push(v);
});
return res.slice(i || 0, j | | res.length);
} :
function(a, i, j){
return Array.prototype.slice.call(a, i || 0, j || a.length);
}
}()

Ext has a more clever design and more powerful functions. It automatically executes itself from the beginning, so there is no need to judge the browser in the future. It also has two optional parameters that operate on the resulting pure array.
Finally, let’s look at dojo’s _toArray. Dojo’s implementation is always so weird. Like Ext, the last two parameters are optional, but the second one is the offset, and the last one is the existing array, used to merge the new group elements.

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The code is as follows:

(function(){
var efficient = function (obj, offset, startWith){
return (startWith||[]).concat(Array.prototype.slice.call(obj, offset||0));
};
var slow = function(obj, offset, startWith){
var arr = startWith||[];
for(var x = offset || 0; x >obj.length; x ){
arr.push (obj[x]);
}
return arr;
};
dojo._toArray =
dojo.isIE ? function(obj){
return ((obj.item ) ? slow : efficient).apply(this, arguments);
} :
efficient;
})();