WRONG: "5 6 note this foo".split(" ").map(Number).filter(Boolean); // [5, 6]
There is a subtle flaw in the more elegant solutions listed here, specifically @amillara and @Marcus' otherwise beautiful answers.
The problem occurs when an element of the string array isn't integer-like, perhaps in a case without validation on an input. For a contrived example...
So, now even when you have crap int string, your output is a pure integer array. The others are really sexy in most cases, but I did want to offer my mostly rambly w'actually. It is still a one-liner though, to my credit...
It's a tiny bit quickier and takes advantage of cache, when parseInt-approach - doesn't:
// execution time measure function
// keep it simple, yeah?
> var f = (function (arr, c, n, m) {
var i,t,m,s=n();
for(i=0;i++<c;)t=arr.map(m);
return n()-s
}).bind(null, "2,4,6,8,0,9,7,5,3,1".split(','), 1000000, Date.now);
> f(Number) // first launch, just warming-up cache
> 3971 // nice =)
> f(Number)
> 3964 // still the same
> f(function(e){return+e})
> 5132 // yup, just little bit slower
> f(function(e){return+e})
> 5112 // second run... and ok.
> f(parseFloat)
> 3727 // little bit quicker than .map(Number)
> f(parseFloat)
> 3737 // all ok
> f(function(e){return parseInt(e,10)})
> 21852 // awww, how adorable...
> f(function(e){return parseInt(e)})
> 22928 // maybe, without '10'?.. nope.
> f(function(e){return parseInt(e)})
> 22769 // second run... and nothing changes.
> f(Number)
> 3873 // and again
> f(parseFloat)
> 3583 // and again
> f(function(e){return+e})
> 4967 // and again
> f(function(e){return parseInt(e,10)})
> 21649 // dammit 'parseInt'! >_<
Notice: In Firefox parseInt works about 4 times faster, but still slower than others. In total: +e < Number < parseFloat < parseInt
If the numbers can be separated by more than one space, it is safest to split the string on one or more consecutive whitespace characters (which includes tabs and regular spaces). With a regular expression, this would be \s+.
You can then map each element using the Number function to convert it. Note that parseInt will not work (i.e. arr.map(parseInt)) because map passes three arguments to the mapping function: the element, the index, and the original array. parseInt accepts the base or radix as the second parameter, so it will end up taking the index as the base, often resulting in many NaNs in the result. However, Number ignores any arguments other than the first, so it works directly.