javascript - 使用reduce.call时累加器未初始化

Question

为什么我的累加器没有初始化？我总是变得不确定。

var S = "SOSSTSROS";

var radiatedLetters = Array.prototype.reduce.call(S,function(acc,curr){
    if(!curr.match(/[SO]/)){
        acc++;            
    }
},0);
console.log(radiatedLetters);

Answer 1

您需要return the accumulated value from the reducer function ，不改变它:

var S = "SOSSTSROS";

var radiatedLetters = Array.prototype.reduce.call(S, function(acc, curr) {
  if (!curr.match(/[SO]/)) {
    return acc + 1;
  } else {
    return acc;
  }
}, 0);
console.log(radiatedLetters);