I have a few arrays with like names.
ArrayTop[]
ArrayLeft[]
ArrayRight[]
ArrayWidth[]
I am trying to set the name dynamically in a function and then set value.
I have tried many ways of dynamically picking the right array but have not come up with a solution.
function setarray(a,b,c){
eval(Array+a+[b])=c
}
setarray('Top',5,100)
In this example i am trying to set.
ArrayTop[5]=100
If you are doing this in the browser, one possible solution would be to do:
function setArray(a, b, c){
window['Array' + a][b] = c;
}
setArray('Top', 5, 100);
I would recommend that all your array's be contained in some object and not pollute the global namespace. So it would be more like:
var arrays = {
ArrayTop: [],
ArrayNorth: []
};
function setArray(a, b, c){
arrays['Array' + a][b] = c;
}
setArray('Top', 5, 100);
I would not recommend using eval. Eval is not meant for this kind of dynamic evaluation and it is a huge performance hit.
Hash map will be a perfect tool:
var arrays = {
top: [],
left: [],
right: [],
bottom: []
};
function addToArray(name, index, value) {
arrays[name][index] = value;
}
addToArray('top', 5, 100);
I took the liberty to give more explicit names.
I suggest also two good practices:
do not use eval. Eval is not meant for this kind of dynamic evaluation. In your case, it's a performance killer
do not polute the global namespace. In browser environnement, avoid adding stuff to window (which is global).
Why not indexing your array with an object?
var arrayNames=["top","left","right","bottom"]
var data=[1,2,3,4,5];
var arrays={};
arrayNames.forEach(function(x){
arrays[x]=data;
});
So you could get your Array via Name. If you randomize or autogenerate the names, no prob.
Put all your arrays into an object:
var myArrays = {
top : arrayTop,
left: arrayLeft,
right: arrayRight,
bottom: arrayBottom
}
And the to get an array you can just:
myArrays["top"][5] = 100;
Or you can skip defining the arrays as global variables and just do something like:
var myArrays = {
top : [],
left: [],
right: [],
bottom: []
}
Which initializes 4 empty arrays which you can populate:
myArrays["top"][0] = 100;
or
myArrays.top[0] = 100;
However, if top, left, right and bottom all are related (refering to the same object), it might make more sense to create an object with those properties and create a single array of those objects:
function MyObj(top, left, right, bottom) {
this.top = top;
this.left = left;
this.right = right;
this.bottom = bottom;
}
var myArray = [];
myArray.push(new MyObj(1,2,3,4));
console.log(myArray[0]);
myArray[0].left = 7;
console.log(myArray[0]);
You can do it this way:
function setarray(a,b,c){
window['Array' + a][b] = c;
}
setarray('Top',5,100)
However, you shouldn't be doing this. Use a 2D array or an object or something. The purpose of this answer is just to show that it CAN be done, not that it SHOULD be done.
ArrayTop[0] and ArrayLeft[0] are related which might not be the case. They probably are, but there isn't enough context in the question. If they are, I'd say use a single array of objects with a top, left, right and bottom properties.
You missed, that Array has to be a String => "Array". Then you can do
var postfix = "Top";
var a = eval("new Array"+postfix);
a.push(100);
try something like this
var someArr = {
};
someArr.ArrayTop = [];
function setarray(a, b, c) {
var arrName = "Array" + a;
someArr[arrName][b] = c;
}
setarray('Top', 5, 100)
alert(someArr.ArrayTop[5]);
Hope this works. Here is the fiddle
