How do you easily create empty matrices javascript?

Question

In python, you can do this:

[([None] * 9) for x in range(9)]

and you\'ll get this:

[[None, None, None, None, None, None, No         


        

Answer 1

Here's one, no looping:

(Math.pow(10, 20)+'').replace((/0/g),'1').split('').map(parseFloat);

Fill the '20' for length, use the (optional) regexp for handy transforms and map to ensure datatype. I added a function to the Array prototype to easily pull the parameters of 'map' into your functions.. bit risky, some people strongly oppose touching native prototypes, but it does come in handy..

    Array.prototype.$args = function(idx) {
        idx || (idx = 0);
        return function() {
            return arguments.length > idx ? arguments[idx] : null;
        };
    };

// Keys
(Math.pow(10, 20)+'').replace((/0/g),'1').split('').map(this.$args(1));
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

// Matrix
(Math.pow(10, 9)+'').replace((/0/g),'1').split('').map(this.$args(1)).map(this.$args(2))