js_字符串去重

 1 var str = 'abcaedijsalpa'
 2       var num = 0
 3       var index = str.indexOf('a')
 4       while (index !== -1) {
 5         console.log(index)
 6         num++
 7         index = str.indexOf('a', index + 1)
 8         // console.log(index)
 9       }
10       console.log(num)