采用遍历的方法获取字符串a在字符串b中的位置

String.prototype.place= function (val) {
var rst = -1;
for (var i = 0; i < this.length; i++) {
if (val[0] == this[i]) {
var temp = i;
if (rst != -1) {
return rst;
}
for (var j = 0; j < val.length; j++) {
if (val[j] == this[temp++]) {
rst = i;
}else{
rst = -1;
}
}
}
}
return rst;

}