Variables should be declared with ‘let’ or ‘const’

Why you should care

The distinction between the variable types created by var and by let is significant, and a switch to let will help alleviate many of the variable scope issues which have caused confusion in the past.

This code insight will trigger when var is used instead of const or let.

How we detect

CAST Highlight counts one occurrence each time a variable is declared using the var statement.

Bad Code

var color = "blue";
var size = 4;

Good Code

const color = "blue";
let size = 4;



About CAST and Highlight’s Code Insights

Over the last 25 years, CAST has leveraged unique knowledge on software quality measurement by analyzing thousands of applications and billions of lines of code. Based on this experience and community standards on programming best practices, Highlight implements hundreds of code insights across 15+ technologies to calculate health factors of a software.