Blob API
The Blob API is used to process binary data, and can easily convert data to or read data from Blob objects.
// 创建一个Blob对象
const myBlob = new Blob(["Hello, world!"], { type: "text/plain" });
// 读取Blob对象的数据
const reader = new FileReader();
reader.addEventListener("loadend", () => {
console.log(reader.result);
});
reader.readAsText(myBlob);Usage scenario: In web applications, binary files may need to be uploaded or downloaded, and these data can be conveniently processed using the Blob API.
WeakSet
A WeakSet is similar to a Set, but can store weakly referenced objects. This means that if there are no other references pointing to an object, then the object can be reclaimed by the garbage collector without having to be manually removed from the WeakSet.
const myWeakSet = new WeakSet();
const obj1 = {};
const obj2 = {};
myWeakSet.add(obj1);
myWeakSet.add(obj2);
console.log(myWeakSet.has(obj1)); // true
obj1 = null;
console.log(myWeakSet.has(obj1)); // falseUsage scenario: In some cases, you may need to store some temporary objects, but you don't want these objects to take up too much memory. These objects can be easily managed using WeakSet.
TextEncoder and TextDecoder
TextEncoder and TextDecoder are used to handle the conversion between strings and byte sequences. They are handy for encoding a string to a sequence of bytes or decoding a sequence of bytes to a string.
const encoder = new TextEncoder();
const decoder = new TextDecoder();
const myString = "Hello, world!";
const myBuffer = encoder.encode(myString);
console.log(myBuffer); // Uint8Array(13) [72, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100, 33]
const decodedString = decoder.decode(myBuffer);
console.log(decodedString); // "Hello, world!"Usage scenario: In web applications, it may be necessary to convert strings to binary data, or convert binary data to strings. These conversions are conveniently done using TextEncoder and TextDecoder.
Proxy API
Proxy API can be used to create proxy objects, which can intercept operations such as reading and assigning object properties. This function can be used to implement functions such as metaprogramming and data hijacking
const myObject = {
name: "John",
age: 30,
};
const myProxy = new Proxy(myObject, {
get(target, property) {
console.log(`Getting property ${property}`);
return target[property];
},
set(target, property, value) {
console.log(`Setting property ${property} to ${value}`);
target[property] = value;
},
});
console.log(myProxy.name); // "John"
myProxy.age = 31; // Setting property age to 31Usage scenario: In some cases, it may be necessary to intercept operations such as reading and assigning object properties to achieve more advanced functions. These functions can be easily implemented using the Proxy API.
Object.entries() 和 Object.values()
Object.entries() is used to get an array of an object's enumerable properties and values, and Object.values() is used to get an array of an object's enumerable property values.
const myObject = {
name: "John",
age: 30,
};
console.log(Object.entries(myObject)); // [["name", "John"], ["age", 30]]
console.log(Object.values(myObject)); // ["John", 30]Usage scenario: In some cases, it may be necessary to obtain the enumerable properties or property values of an object. These functions can be easily implemented using Object.entries() and Object.values().
IntersectionObserver
IntersectionObserver can be used to detect whether an element enters the viewport, and can be used to implement functions such as infinite scrolling and lazy loading.
const myObserver = new IntersectionObserver((entries, observer) => {
entries.forEach((entry) => {
if (entry.isIntersecting) {
console.log(`${entry.target.id} is now visible`);
observer.unobserve(entry.target);
}
});
});
const myElement = document.getElementById("myElement");
myObserver.observe(myElement);Usage scenario: In web applications, functions such as infinite scrolling and lazy loading may need to be implemented, and these functions can be easily realized by using IntersectionObserver.
Symbol
Symbol can be used to create unique identifiers and can be used to define private properties or methods of objects.
const mySymbol = Symbol("mySymbol");
const myObject = {
[mySymbol]: "This is a private property",
publicProperty: "This is a public property",
};
console.log(myObject[mySymbol]); // "This is a private property"
console.log(myObject.publicProperty); // "This is a public property"Usage scenario: In some cases, it may be necessary to define private properties or methods of objects, which can be easily realized by using Symbol.
Reflect API
The Reflect API can be used to implement metaprogramming, such as dynamically calling methods or constructors of objects.
class MyClass {
constructor(value) {
this.value = value;
}
getValue() {
return this.value;
}
}
const myObject = Reflect.construct(MyClass, ["Hello, world!"]);
const myMethod = Reflect.get(myObject, "getValue");
const myValue = myMethod.call(myObject);
console.log(myValue); // "Hello, world!"Usage scenario: In some cases, it may be necessary to dynamically call the method or constructor of the object, which can be easily realized by using the Reflect API.
Generator API
The Generator API can be used to generate iterators, which can be used to implement asynchronous operations or lazy calculations.
function* myGenerator() {
yield "Hello";
yield "world";
yield "!";
}
const myIterator = myGenerator();
console.log(myIterator.next().value); // "Hello"
console.log(myIterator.next().value); // "world"
console.log(myIterator.next().value); // "!"Usage scenarios: In some cases, it may be necessary to implement asynchronous operations or lazy calculations, and these functions can be easily implemented using the Generator API.
Web Workers
Web Workers can be used to execute JavaScript code in a background thread, which can be used to improve performance or implement complex calculations.
// main.js
const myWorker = new Worker("worker.js");
myWorker.postMessage("Hello, worker!");
myWorker.onmessage = (event) => {
console.log(`Message received from worker: ${event.data}`);
};
// worker.js
onmessage = (event) => {
console.log(`Message received in worker: ${event.data}`);
postMessage("Hello, main!");
};Usage scenario: In web applications, it may be necessary to process a large number of computationally intensive tasks or perform long-running operations. Using Web Workers can improve performance or avoid blocking the user interface.
AudioContext
AudioContext can be used to process audio, and can be used to implement functions such as audio playback and sound effect processing.
const audioContext = new AudioContext();
fetch("https://example.com/audio.mp3")
.then((response) => response.arrayBuffer())
.then((arrayBuffer) => audioContext.decodeAudioData(arrayBuffer))
.then((audioBuffer) => {
const source = audioContext.createBufferSource();
source.buffer = audioBuffer;
source.connect(audioContext.destination);
source.start();
});Usage scenario: In web applications, functions such as audio playback and sound effect processing may need to be implemented, and these functions can be easily realized by using AudioContext.
Summarize
The above Web APIs and their usage scenarios, these APIs can help us realize various functions of Web applications more conveniently. Of course, in addition to these APIs, there are many other useful APIs and tools. It is recommended that you explore more in order to better deal with various challenges of web development.