Postman PreRequest Script Example

getBearer.js

const appEnv = (pm.environment.name);
const userEmail = pm.environment.get('yourloginemail');
const userPass = pm.environment.get('yourloginpassword');

const authBody = {
    grant_type: "password",
    email: userEmail,
    password: userPass,
};

const authRequest = {
    url: `https://{appEnv}/yourauthendpoint`,
    method: 'POST',
    header: 'Content-Type:	application/json',
    body: {
        mode: 'raw',
        raw: JSON.stringify(authBody)
    }
};

pm.sendRequest(authRequest, (err, response) => {
    if (!err) {
        const data = response.json()
        pm.environment.set('accessToken', data['access_token']);
    }
});