The problem is I need to add a multi dimension array dynamically, please look at the following example:
var list = [];
var listname;
var height;
var width;
list.push(listname);
list[listname] = height;
list[listname] = width;
the code above is not what I expected , which should be [listname => [[0]=>height,[1]=>width]], what can I do if I do not want to create an array for listname, can I dynamic add a mulit dimension array ? thanks.
Don't confuse Arrays with Maps. They are different fundamental data-types1
var myLists = {}; // name => array
var listname = "stuff"; // why not?
var height = 1;
var width = 2;
// there is no Object.push, but we can assign a property by name
myLists[listName] = [height];
// then we can Array.push into the array we just assigned
myLists[listName].push(width);
Then, myLists:
{
stuff: [1, 2]
}
1JavaScript mostly maintains this distinction - if one doesn't add random properties to Arrays or otherwise fake an Object to behave like an array.
obj.hasOwnProperty(propName) or propName in obj (when not as for(x in y)) - but they do slightly different things. I prefer the latter (with in) for "existence testing" as it will look up the chain, if it ever matters, and it just "looks cleaner" to me. Also, obj[propname] is sometimes more appropriate, if the value (and whether or not it is truth-y) if also of importance.