JavaScript数组求和的5种常用方法

var arr = [1,2,3];

function sum(arr) {

  var s = 0;

  for (var i = 0;i<arr.length;i++) {

    s += arr[i];

  }

  return s;

}

console.log(sum(arr));//6

var arr = [1,2,3];

function sum(arr) {

  var s = 0;

  arr.forEach(function(val, idx, arr) {

    s += val;

  }, 0);

  return s;

};

console.log(sum(arr));//6

var arr = [1,2,3];

function sum(arr) {

  return arr.reduce(function(acr, cur){

    return acr + cur;

  });

}

console.log(sum(arr));//6

var arr = [1,2,3];

function sum(arr) {

  if(arr.length == 0){

    return 0;

  } else if (arr.length == 1){

    return arr[0];

  } else {

    return arr[0] + sum(arr.slice(1));

  }

}

console.log(sum(arr));//6

var arr = [1,2,3];

function sum(arr) {

  return eval(arr.join("+"));

};

console.log(sum(arr));//6