字符在字符串中出现的次数和位置

var str = 'To be, or not to be, that is the question.';
var count = 0; // 出现的次数
var countArr = []; // 出现的位置

var targetChar = 'e';

// 方法一
var reg = new RegExp(targetChar, 'g');
str.replace(reg, function(item, index){
  count ++;
  countArr.push(index);
  return item;
})
console.log(count, countArr); // 4 [4, 18, 31, 35]

// 方法二
count = 0;
countArr = []];
var pos = str.indexOf(targetChar);
while(pos>=0){
    count ++;
    countArr.push(pos);
    pos = str.indexOf(targetChar, pos+1);
}
console.log(count, countArr); // 4 [4, 18, 31, 35]

// 方法三
count = 0;
countArr = [];
var arr = str.split('');
for(var i=0, len=arr.length; i<len; i++){
    if(arr[i] === targetChar) {
        count++;
        countArr.push(i);
    }
}
console.log(count, countArr); // 4 [4, 18, 31, 35]

• String​.prototype​.replace() -MDN
• String​.prototype​.indexOf()-MDN