I am going through a JS Book (Modern Javascript for the Impatient) and came across this example, which had a different output than what I was expecting.
const numbers = [1, 2, 3]
numbers.forEach(console.log)
1 0 [ 1, 2, 3 ]
2 1 [ 1, 2, 3 ]
3 2 [ 1, 2, 3 ]
When I use a lambda expression like syntax, I see the right (expected) result.
const numbers = [1, 2, 3]
numbers.forEach(number => console.log(number))
1
2
3
How is the expression being evaluated in the first case? Is the lambda expression syntax always expected?
>Solution :
It has nothing to do with arrow function expression (lambda) syntax.
console.log() accepts a series of arguments.
The callback signature for Array.prototype.forEach() is:
forEach((element, index, array) => { /* … */ })
So, for every invocation of the callback (console.log in your example), the series of arguments is displayed in the console.