A brief discussion on loop vs recursion_javascript skills

For example, traverse the following one-dimensional array:

Copy code The code is as follows:

[javascript] view plaincopyprint?
var a1 = [1];
var a2 = [1, 2];
var a3 = [1, 2, 3];

Although they vary in length, it is very easy and elegant to loop through them:

Copy code The code is as follows:

[javascript] view plaincopyprint?
var dumpArrayByLoop = function(a) {
for (var i = 0; i < a.length; i ) {
println(a[i]);
}
};

If you use recursion instead, it will look awkward:

Copy code The code is as follows:

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var dumpArrayByRecur = function(i, a) {
if (i < a.length) {
println(a[i]);
dumpArrayByRecur(i 1, a);
} }
} ;

They output the same result, but the recursive version looks clunky in comparison.

Now think about it, if the metadata changes: the dimension expands to two dimensions.

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var a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];

At this time, you need to add another layer of loop outside to form a double loop:

Copy code The code is as follows:

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var dumpArrayByLoop = function(a) {
for (var i = 0; i < a.length; i ) {
for (var j = 0; j < a[i].length; j ) {
                   println(a[i][j]); Dynamic N-dimensional array. How to deal with using loops?

In this situation where the number of "layers" is very deep or even uncertain, "recursion" needs to be used to solve cross-"layer" problems.

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The code is as follows:[javascript] view plaincopyprint?var isArray = function(a) { return Object.prototype.toString.call(a) === '[object Array]'; };

var dumpArrayByRecur = function(a) {
if (isArray(a)) {
for (var i = 0; i < a.length; i ) {
dumpArray(a[i]);
} else {
println(a);
}
};




In the above code, if the child node is found to be an array, recursion is used to enter the next level; while traversal on the same level is completed using loops.