The 20th blog post of the collection of front-end interview skills - high-frequency test points (the entire process from entering the URL to page rendering)

This is a record 前端面试的话术集锦第二十篇博文——高频考点（输入 URL 到页面渲染的整个流程）and I will keep updating this blog post. ❗❗❗

Use this classic interview question to connect the knowledge you have learned about browsers and network chapters before.

The first is query. If intelligent analysis DNSis done in this step , the address with the fastest access speed will be provided back.DNSIP

1. DNS

DNSThe function is to query specific information through domain names IP.

Because IPthere is a combination of numbers and English ( IPv6), which is not conducive to human memory, domain names appeared. You can think of a domain IPname as an alias, DNSand you want to query the real name of the alias.

TCPThe query has already been performed before the handshake , DNSand this query is done by the operating system itself. When you want to visit www.baidu.com in your browser , you will perform the following operations:

1. The operating system will first query the local cacheIP

2. DNSIf not, it will query the server configured in the system.

3. If it is still not available at this time, it will go directly to DNSthe root server to query. This step of query will find out comthe server responsible for this first-level domain name.

4. Then, go to the server to query baiduthe second-level domain name

5. Next, the third-level domain name query is actually configured by us. You