So the following won't work:
var Foo = {
array1 : ['apples', 'oranges', 'grapes'],
arrayLength : array1.length // error
}
Is there any way I can access Foo.array1's length within the object?
3 Answers
You'll need to do it like this:
var Foo = {};
Foo['array1'] = ['apples', 'oranges', 'grapes'];
Foo['arrayLength'] = Foo['array1'].length;
Or like this (much cleaner IMHO):
var Foo = function() {
var a = ['apples', 'oranges', 'grapes'];
return {'array1': a, 'arrayLength':a.length};
}();
Another alternative:
function Foo(array) {
this.array1 = array;
this.arrayLength = array.length;
//other stuff...
}
var f = new Foo(['apples', 'oranges', 'grapes']);
But really, this doesn't make much sense to me, you're already storing the array, why do you need to cache the length property?`
or:
var x;
var Foo = {
array1 : x = ['apples', 'oranges', 'grapes'],
arrayLength : x.length
};
alert(Foo.arrayLength);
clearly not so nice, the Jacob Relkin' solution is better
1 Comment
Jacob Relkin
If you're going to use a variable, might as well actually assign it in the same line that you define it.
You can't really access a property like that.
You can use a function such as :
var Foo = {
array1 : ['apples', 'oranges', 'grapes'],
arrayLength : function(){ return this.array1.length;}
}
which is actually a good thing and I recommend using this since the Foo.array1 array can change in time, and you probably want the arrayLength field to be updated.
Another option would be to use a closure that returns your object literal :
var Foo = (function(){
var array1 = ['apples', 'oranges', 'grapes'];
return {
array1 : array1,
arrayLength : array1.length
};
})();
If you really want to get into oop stuff, you can use "constructors" and prototypes for this :
var FooClass = function(array){this.init(array);}
FooClass.prototype = new function(){
this.init = function(array){
this.array1 = array;
this.updateArrayLength();
};
this.updateArrayLength = function(){
this.arrayLength = this.array1.length;
};
this.array1 = [];
this.arrayLength = 0;
};
var Foo = new FooClass(['apples', 'oranges', 'grapes']),
Foo2 = new FooClass(['bananas', 'limes', 'grapefruits']);
1 Comment
Jacob Relkin
I happened to have already suggested your second example in my answer.