moy-fp/src/List/findIndex.js

A functional programming library.

import curry from '../Function/curry'

/**
 * (a -> Boolean) -> [a] -> Number
 */
const findIndex = curry(
  (pred, list) => {
    const entries = list.entries()
    for(let [index, item] of entries){
      if(pred(item)){
        return index
      }
    }
    return -1
  }
)

export default findIndex