Immutable & Pure Functions

@Antoine addMulti=(x, multi)=>x+multi is not the example given in this video. Both functions you have provided are pure because they will always return the same value given the same parameters, the only thing different is the naming of the function and the second parameter. Let me know if you need more clarification on this.

But const addMulti=(x, multi)=>x+multi; is pure, it would be const add=(x,y)=>x+y, it always do the same thing, it adds the two arguments.