PHP会话如何工作？(How do PHP sessions work? (not “how are they used?”))

 您仍然需要首先实例化它。 使用JavaScript测试： 
 
var web3 = new Web3();
window.console.log(web3);
> Object { _requestManager: Object, currentProvider: undefined, eth: 
    Object, db: Object, shh: Object, net: Object, personal: Object, bzz: 
    Object, settings: Object, version: Object, 2 more… }
 
 我没有使用TypeScript的经验，但你明白了。 web3js提供了库，您需要初始化它才能使用。 它基本上是链接文档页面的第一行。 

You still need to instantiate it first. Tested with JavaScript:
 
var web3 = new Web3();
window.console.log(web3);
> Object { _requestManager: Object, currentProvider: undefined, eth: 
    Object, db: Object, shh: Object, net: Object, personal: Object, bzz: 
    Object, settings: Object, version: Object, 2 more… }
 
I have no experience with TypeScript though, but you get the idea. web3js is providing the library, and you need to initialize it to work with. It's basically the first line of the linked documentation page.