javascript join array to another

Question

I want to write a function to join an array to another but different way :

var myNumbers = [10,20,3,4,2]
var myOperations = ['+','-','*','/']

I want the operators locate between myNumbers element : 10+20-3*4/2 = 54

thank you

Welcome to Stack Overflow ! Please read the [tour], [help] and [ask]. Users are expected to show their attempts or research in their question, to ensure a better reception. — Pac0, Sep 18 '19 at 08:11

score 0 · Answer 1 · edited Sep 18 '19 at 08:26

0

Just Change the var str = 0 to str = ''

var myNumbers = [10,20,3,4,2]
var myOperations = ['+','-','*','/'];
var str = '';
for(var i = 0 ; i < myNumbers.length ; i++){
  if(myOperations[i]){
    str += myNumbers[i] + myOperations[i]; 
  }else{
    str += myNumbers[i];
  }
}
console.log(str);

edited Sep 18 '19 at 08:26

MUKUL VERMA

33
3

answered Sep 18 '19 at 08:16

Pushprajsinh Chudasama

7,772
4
20
43

`010+20-3*4/2`? – CodeRed Sep 18 '19 at 08:17
that `010` , the `0` before `10` is will not considered in calculatoin . @CodeRed – Pushprajsinh Chudasama Sep 18 '19 at 08:18
Point taken. But can syntactically be avoided. – CodeRed Sep 18 '19 at 08:21
Yess i can be . @CodeRed – Pushprajsinh Chudasama Sep 18 '19 at 08:21
@PushprajsinhChudasama Depends a bit on how the calculation is done. `eval('010')` will return `8`. – Ivar Sep 18 '19 at 08:22
@Ivar, that is why I am telling PushprajsinhChudasama that it could be avoided – CodeRed Sep 18 '19 at 08:24
@CodeRed Yes, sorry, annotated the wrong person. – Ivar Sep 18 '19 at 08:24
@Ivar all is well brother – CodeRed Sep 18 '19 at 08:25

GBouffard · Answer 2 · 2019-09-18T08:44:00.570

Some duplicates questions have already been pointed by other members and they could have helped you. Please find below a solution that I worked out for your problem.

var numbersAndOperations = myNumbers.map((a, i) => myOperations[i] ? [a, myOperations[i]] : [a])
/* this makes a 2 levels deep array from your 2 and avoids any undefined values through a ternary operator.
If you don't know ternary operators they are a shorthand for an if condition.
[[10, "+"], [20, "-"], [3, "*"], [4, "/"], [2]] */

const myMathString = numbersAndOperations.flat(2).join(',').replace(/,/g, '')
// this turns it into a string and remove the comas: "10+20-3*4/2"

function mathEval(mathString) { // this hack evaluates your math function and immediately returns a result.
  return new Function('return ' + mathString)();
}

console.log(mathEval(myMathString)); // 24. The result is actually 24 because * and / are evaluated before the + and -

Hope that it helps :)

javascript join array to another

2 Answers2