Javascript的有状态正则表达式

正则表达式是有状态的

var res, text = "name leo1 leo2 leo3",
    regexp = /leo(\d)/g;


console.log("regexp.lastIndex:", regexp.lastIndex);
while (res = regexp.exec(text)) {
    console.log("regexp.lastIndex:", regexp.lastIndex,
        "index:", res.index,
        "res[0]:", res[0],
        "res[1]:", res[1]);
}
console.log("regexp.lastIndex:", regexp.lastIndex);

regexp.lastIndex: 0
regexp.lastIndex: 9 index: 5 res[0]: leo1 res[1]: 1
regexp.lastIndex: 14 index: 10 res[0]: leo2 res[1]: 2
regexp.lastIndex: 19 index: 15 res[0]: leo3 res[1]: 3
regexp.lastIndex: 0