Uncaught ReferenceError: Web3 is not defined

[Alex-Gorbach]

Hello! I'm trying to create an instance of web3 using the following code in the index.js file:
var web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'));
But have an error:

I have installed Web3 and started the testrpc.
When I execute this code in the node.js terminal , there are no errors.
Why is this happening? Thanks.

[nisdas]

Most likely you did not import the web3 library using this : var Web3 = require("web3")
Do that and you should be fine

[Alex-Gorbach]

var Web3 = require("web3") also produced an error: "Uncaught ReferenceError: require is not defined".
I solved this problem using the following construction from here:
if (typeof web3 !== 'undefined') { web3 = new Web3(web3.currentProvider); } else { // set the provider you want from Web3.providers web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545")); }
Thanks.

[ddb1]

i have also meet this problem ,who can tell me how to solve it. thanks!