What is the most elegant way to generate a numerical sequence like 1,-1,1,-1

Question

I have a for loop and inside I'd like to get a sequence like 1,-1,1,-1... (The loop does other things also so I don't want to alter the loop itself)

For now I have a solution like below, but there must be some more elegant way to do this I think :)

let plusMinus = [-1, 1]

for (let i = 0; i < 10; i++) {
  console.log(plusMinus[i % 2])
}

For me it's fewer lines, no redundant variables like `plusMinus` in my case. The best answer for me that I saw below was probably `console.log(Math.pow(-1, i))` but it is now gone. — Picard, Mar 14 '18 at 08:31
that requires alwaays a mathematical operationb for a toggled value. maybe it is mor a question about do you want a value for an arbitrary value of `i`? then you could use `i % 2 || -1` without an array. — Nina Scholz, Mar 14 '18 at 08:38
Thanks @NinaScholz this is even better than the `Math.pow` because it uses only simple operators - I knew there should be such simple solution but I couldn't figure it out! — Picard, Mar 14 '18 at 09:05

score 1 · Answer 1 · answered Mar 14 '18 at 06:57

1

 let state = 1;
 for (let i = 0; i < 10; i++) 
    console.log(state = -state)

answered Mar 14 '18 at 06:57

Jonas Wilms

score 1 · Answer 2 · answered Mar 14 '18 at 06:57

1

Use Array.from :

var length = 5;
var sequence = Array.from(Array(length), (x, i) => i % 2 ? -1 : 1);
console.log(sequence);

answered Mar 14 '18 at 06:57

Faly

2 Answers2