您可以使用lodash函数来完成此操作。

const res = pm.response.json();
let sites = _.map(res, _.property("site"));

//or
let sites = _.map(res, "site"));

//Set as environment variable  
    var sites = response.json()["sites"];
    pm.environment.set("sites", sites);

//Set as global variable  
    var sites = response.json()["sites"];
    pm.globals.set("sites", sites);

//Set as collection variable  
    var sites = response.json()["sites"];
    pm.collectionVariables.set("sites", sites);