Test-Driven React

Checking Code Quality with ESLint

A linter is a program that uses a set of rules to detect code that, though syntactically valid, is likely to contain mistakes. A classic example is using = (assignment) instead of == or === (equality) in an if statement:

if (savings = 0) {
  // This "condition" would empty your account!
}

Linting JavaScript is especially valuable because of its relatively freewheeling nature. If you mistype window as wimdow, your program won’t refuse to run; it just won’t run the way you’d hoped. Of course, one way to avoid such fat-finger bugs is to have extensive test coverage. But a linter can often identify such problems sooner, and give you more helpful information for fixing them. Enter ESLint.^[24]

Although other ...