How to console log the name of a variable/function?

Question

I want to do this: log(variableOrFunction)

And be able to produce this: variableOrFunction: actualValue.

I tried this:

Answer 1

You can’t achieve this within the JS interpreter the way you have described. There is no way to get the name of a variable inside of your log function.

You can only do it inside of the caller of your log function, by converting the calling function to a string and parsing the code and grabbing the variable name passed to your log function.

You could try to get the caller of the log function and do what I have described but I would not recommend this.

Answer 2

If “value” is of type Object. You can try console.dir(value) instead of the long console.log, and you should be able to see the Object tree key: value pairs in a better formate in the console

Answer 3

You can log them with a pair of braces around them ({}), which will create an object with the name of the variable as the key:

function someFunction() {};

const someOtherFunction = () => {};

const someValue = 9;

console.log({someFunction});
console.log({someOtherFunction});
console.log({someValue});

const renamed = someFunction;

console.log({renamed})

Answer 4

Would this work for you?

const log = function() {
  const key = Object.keys(this)[0];
  const value = this[key];
  console.log(`${key}:${value}`);
}

let someValue = 2;

log.call({someVlaue}); //someValue:2

Works with function too, even itself.

log.call({log});

// It would return the following
log:function() {
  const key = Object.keys(this)[0];
  const value = this[key];
  console.log(`${key}:${value}`);
}

Answer 5

The "value" is of type Object. Use JSON.stingify to see in details,

export const log = (value) => {
  console.log('' + value + ':', JSON.stringify(value))
  console.log(JSON.stringify(value))
}

Answer 6

Built on @CRice answer:

const arr = [10, 20, 30, 40, 50]
const obj = { a: 10, b: 20, c: 30, d: { e: 40 } }
const str = "abcdef"

function slog(obj) {
  Object.entries(obj).forEach(([key, value]) => console.log(key + ":", value))
}

slog({ arr })  // arr: [ 10, 20, 30, 40, 50 ]
slog({ obj })   // obj: { a: 10, b: 20, c: 30, d: { e: 40 } }
slog({ str })   // str: abcdef