Promise You Will Love It

JavaScript Promises Have Arrived

What makes a good library great? The ability to chain and group asynchronous operations!

SpRestLib not only provides a simple REST interface, it also delivers next-generation async operation handling via ES6 Promises.

Simple Chains For Async Operations

SharePoint applications frequently perform lots of operations (e.g.: read from many lists at startup) or perform sequential steps (e.g.: get an item, then do further operations depending upon the result). Until recently, using callbacks was the standard way to handle async completion, but with Promises (which all SpRestLib methods return) operations can be easily chained by using then(), making your code much easier to write and maintain.

See the Async Operations via Promises section for more information and examples.

Promises Example

// EX: Get the current user's ID, then get their Tasks
sprLib.user().info()
.then(function(objUser){
    return sprLib.list('Tasks').items({ queryFilter:'Owner/Id eq ' + objUser.Id });
})
.then(function(arrItems){
    console.log("Current user's Tasks = " + arrItems.length);
})
.catch(errMsg => console.error(errMsg));

Async/Await Example

You can also use the native async/await syntax as async/await is built on JavaScript Promises.
(Available in recent browsers, Node.JS 8.6+, or via transpiling with BabelJS)

Async/Await makes using SpRestLib even simplier as the asynchronous nature of web service calls is masked by the abilty to declare a variable against an operation that will run in the background, etc. Meaning you can write code that runs in a "normal", linear fashion as shown below.

const infoGetter = async() => {
    // EX: Get the current user's ID, then get their Tasks
    const objUser = await sprLib.user().info();
    const arrItems = await sprLib.list('Tasks').items({ queryFilter:'Owner/Id eq ' + objUser.Id });
    console.log("Current user's Tasks = " + arrItems.length);
}