Equilibrium Index

equilibrium-index.js

// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');

function solution(A) {
    let sum = null,
    previous_sum = 0,
    next_sum = null;
    
    if(!A || A.length === 0) {
        return -1;
    } else if(A.lengh === 1) {
        sum = A[0];
    } else {
        sum = A.reduce((total, num)=>{
            return total + num;
        })
    }
    
    for(let i = 0; i < A.length; i++) {
        next_sum = sum - previous_sum - A[i];
        
        if(previous_sum === next_sum) {
            return i;    
        }
        
        previous_sum += A[i];
        
    }
    
    return -1;
    
}

solution([-7, 1, 5, 2, -4, 3, 0]);

document.querySelector('#result').innerHTML = solution([-7, 1, 5, 2, -4, 3, 0]);