SOURCE

let expr = "{{person.name}} --- {{person.age}}";
let flag = 0;
let value = expr.replace(/\{\{(.+?)\}\}/g, (a,b,c,d,e) => {
        console.log(a,b,c,d,e);
        console.log('匹配到的字符串', a);
        console.log('回调函数返回替换的值', b);
        console.log('匹配字符串对应索引的位置', c);
        console.log('原始字符串--->', d);
        console.log(++flag);
        return 123;
});
console.log('最后的返回值：', value);