Retrieving Access Token for Service Account using Javascript
This is a sample script for retrieving the access token for Service Account using Javascript. The flow for using this script is as follows.
- At first, please create the Service Account and retrieve JSON file.
- Put Scopes,
private_keyandclient_emailto the script. - Run the script.
Sample script
In this script, 2 libraries of jsencrypt and crypto-js are used.
<script src="https://cdnjs.cloudflare.com/ajax/libs/jsencrypt/3.0.0-rc.1/jsencrypt.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/4.0.0/crypto-js.min.js"></script>
<script>
async function sample() {
const private_key = "###"; // private_key of JSON file retrieved by creating Service Account
const client_email = "###"; // client_email of JSON file retrieved by creating Service Account
const scopes = ["https://www.googleapis.com/auth/drive.readonly"]; // Scopes
const url = "https://www.googleapis.com/oauth2/v4/token";
const header = { alg: "RS256", typ: "JWT" };
const now = Math.floor(Date.now() / 1000);
const claim = {
iss: client_email,
scope: scopes.join(" "),
aud: url,
exp: (now + 3600).toString(),
iat: now.toString(),
};
const signature =
btoa(JSON.stringify(header)) + "." + btoa(JSON.stringify(claim));
const sign = new JSEncrypt();
sign.setPrivateKey(private_key);
const jwt =
signature + "." + sign.sign(signature, CryptoJS.SHA256, "sha256");
const params = {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({
assertion: jwt,
grant_type: "urn:ietf:params:oauth:grant-type:jwt-bearer",
}),
};
const obj = await fetch(url, params)
.then((res) => res.json())
.catch((err) => console.log(err));
console.log(obj);
}
sample();
</script>
If the access token retrieved at above is used for retrieving file list, the sample script is as follows.
