Console

console.X() methods return undefined

console.table

If we have an array of identically formatted objects, we can print out a nice table to the console, instead of getting a dump of a JSON-like structure, as we would have with a simple console.log

console.group

console.dir(obj)

Displays an interactive list of the properies of the passed object

• "interactive" here means that the properties (listed as a hierarchy) can be collapsed and expanded.

console.time/console.timeEnd

We can use this to get the time of how long something takes to execute:

console.time('filter array');
const visibleTodos = getFilteredTodos(todos, filter);
console.timeEnd('filter array'); // filter array: 0.15ms

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Console.log an arrow function

One of the pain points of implicitly returning arrow functions is that you can't easily stick a console.log in, without converting it to an explicit return. To get around this, we can have the function return console.log(myVal) || <rest of the code>. The reason this works is because console methods return undefined, which causes <rest of the code> to continue to be executed.

// Before: 
const myFunc = () => doTheThing()

// After:
const myFunc = () => console.log(myVal) || doTheThing()