Useful tricks for logging debugging information to the browser console

During debugging you might pepper your code with lines like these:

console.log('foo = ' + foo + ', bar = ' + bar)

I recommend to use variable interpolation instead:

console.log('foo = %o, bar = %o', foo, bar)

This has some advantages:

  1. It's easier to write
  2. Variables are colored in the console output
  3. You don't need to stringify arguments so the + operator doesn't explode
  4. If the variable is a structured object like a DOM element or an object has, you will be able to expand it inside the console and look at its contents

Another concise way to write the statement is this:

console.log({ foo, bar });

This uses Javascript's new destructuring syntax Show archive.org snapshot and is actually shorthand for:

console.log({ foo: foo, bar: bar });

Like above, you will be able to expand this object inside the console and look at its contents.

Henning Koch Over 8 years ago