Possible Duplicate:
JavaScript: min & max Array values?
var test = [-42, 0, 8];
var biggest=-Infinity;
for (i=0; i<test.length;i++)
{if (test[i]>biggest)
alert('It is!');
biggest = test[i];
else
alert("It isn't!");}
alert("The biggest element is:" + biggest);
I'm trying to write a program to find the biggest number in an array but my code is not working. Any help please?
You have been bitten by the "too few braces" bug:
if (test[i]>biggest)
alert('It is!');
biggest = test[i]; // THIS IS NOT INSIDE THE IF!
If you fix this, it works just fine.
Of course, you can do this much easier using Math.Max, as this MDN documentation sample shows:
function getMaxOfArray(numArray) {
return Math.max.apply(null, numArray);
}
This is a bit clever, but quite succinct and works well.
Just call apply() on Math.max() and pass the array as the arguments.
var maxValue = Math.max.apply(null, arr);
An alternative solution
function nsort(a,b){
return a - b;
}
var test = [-42, 0, 8, 3, 15, 12],
max = test.sort(nsort).pop(); // 15
Although you should listen to @alex, this is how you would have done it if there were no Math.max, and you wanted to code C-style:
var test = [-42, 0, 8];
var biggest = -Infinity;
for(var i = 0; i < test.length; ++i)
if(test[i] > biggest)
biggest = test[i];
alert("The biggest element is:" + biggest);
Array, you want only the numerical indices.foreach()?ECMAScript 5th Edition introduces a few higher-order functions for arrays -- yay!.
One is Array.reduce (also known as left fold):
Thus, this can be solved as:
var arr = [-42, 0, 8]
var res = arr.reduce(function (prev,cur) {
return cur > prev ? cur : prev
}, -Infinity)
res // 8
Not nearly as "elegant" in this case as applying the array as the parameters to Math.max, but higher-order functions can make good additions to a "toolbox" ;-) Consider the slight modification to find the longest string in an array:
var arr = ["Hello", "World!!!", "Wut?"]
var res = arr.reduce(function (prev,cur) {
return cur.length > prev.length ? cur : prev
}, "")
res // "World!!!"
Try that with Math.max or Array.sort and index/pop ;-)
Happy coding.
While the above is for 5th Edition, a trivial reduce function can be written for ECMAScript 3rd Edition (aka JavaScript 1.5) and equivalent functionality is part of a number of libraries:
function reduce (arr, fn, v) {
for (var i = 0; i < arr.length; i++) {
v = fn(v, arr[i])
}
return v
}
// used as:
reduce(arr, function (prev,cur) { ... }, initValue)
(This could be added to the Array prototype, but I consider mucking with core prototypes fairly ugly.)
test.sort()[test.length-1], just another idea if you're shure it's all numbers.pop()?unshift()then for the lowest value.sort()converts to strings first, then sorts lexicographically, so you will get not a numeric sort. jsFiddle.