In this post, I am going to explain how to iterate over the elements of Array and explain the drawbacks in every approach.
Let me start with basic approach.
var arr1 = [2, 3, 5, 7];
for(var i=0; i
document.write(arr1[i] + "
");
");
}
traversal.html
"text/javascript">
var arr1 = [2, 3, 5, 7];
for (var i = 0; i arr1.length; i++) {
document.write(arr1[i] + "
");
}
What if your array is sparse. If your array is sparse and you use the above approach, you will get lot of undefined values.
traversal.html
"text/javascript">
var arr1 = [2, 3, 5, 7];
arr1[10] = 1234;
for (var i = 0; i arr1.length; i++) {
document.write(arr1[i] + "
");
}
Open above page in browser, you will get following text.
2
3
5
7
undefined
undefined
undefined
undefined
undefined
undefined
1234
One way to resolve this problem is escape all the undefined values.
for(var i=0; i
if(!arr1[i])
continue;
document.write(arr1[i] + "
");
");
}
traversal.html
"text/javascript">
var arr1 = [2, 3, 5, 7];
arr1[10] = 1234;
for (var i = 0; i arr1.length; i++) {
if (!arr1[i])
continue;
document.write(arr1[i] + "
");
}
Open above page in browser, you can able to see following text.
2
3
5
7
1234
One problem with above program is, it escapes null values also. If you are specific about escaping only undefined values, you need to update logic like below.
traversal.html
"text/javascript">
var arr1 = [2, null, 5, 7, null];
arr1[10] = 1234;
for (var i = 0; i arr1.length; i++) {
if (arr1[i] === undefined)
continue;
document.write(arr1[i] + "
");
}
Open above page in browser, you can able to see following text.
2
null
5
7
null
1234
Can I use fo-in loop to traverse array?
One problem with for-in loop is it traverse inherited properties also. If you want to traverse and skip inherited properties update your logic like below.
for(var i in arr1){
if (!arr1.hasOwnProperty(i))
continue;
document.write(arr1[i] + "
");
");
}
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This post first appeared on Java Tutorial : Blog To Learn Java Programming, please read the originial post: here
