JavaScript – Optimize Loops

Performance

Warning

All

Rule number #

SN-0104

Impact #

Evaluating the length of an array each time it is iterated through is inefficient.

Remediation #

Store the length of the array in a variable and use the variable in the evaluation statement.

Time to fix

10 min

Code examples #

Noncompliant code

var names = [‘George’, ‘Ringo’, ‘Paul’, ‘John’]; for(var i=0;i<names.length;i++){ doSomethingWith(names[i]); }

Compliant code

var names = [‘George’, ‘Ringo’, ‘Paul’, ‘John’]; for(var i=0,j=names.length;i<j;i++){ doSomethingWith(names[i]); }