node . js | util . types . isdata view()方法
原文:https://www . geesforgeks . org/node-js-util-types-isdata view-method/
util 模块的 util.types.isDataView()方法方法主要是为了支持 Node.js 自身内部 API 的需求而设计的。 使用 util.types.isDataView()方法检查给定值是否为 DataView 对象。
语法:
util.types.isDataView(value)
参数:该函数接受一个参数,如上所述,如下所述:
- 值:是将为数据视图对象检查的值。
返回值:如果传递的值是数据视图的实例,该方法返回一个布尔值,即真,否则返回假。
下面的程序说明了 Node.js: 中的 util.types.isDataView()方法
例 1:
Node.js
// Node.js program to demonstrate the
// util.types.isDataView() method
// Import the util module
const util = require('util');
// Checking for a DataView
let arraybuf = new ArrayBuffer(5);
let dataView = new DataView(arraybuf);
console.log("Value:", dataView);
isDataView = util.types.isDataView(dataView);
console.log("Value is a DataView:", isDataView);
// Checking for an Integer array
let intArray = new Int32Array();
console.log("Value:", intArray);
isDataView = util.types.isDataView(intArray);
console.log("Value is a DataView:", isDataView);
输出:
Value: DataView {
byteLength: 5,
byteOffset: 0,
buffer: ArrayBuffer { [Uint8Contents]:
<00 00 00 00 00>, byteLength: 5 }
}
Value is a DataView: true
Value: Int32Array []
Value is a DataView: false
例 2:
Node.js
// Node.js program to demonstrate the
// util.types.isDataView() method
// Import the util module
const util = require('util');
// Creating an unsigned integer 8-bit array
let int8Array = new Uint8Array([10, 20, 30]);
console.log("Value:", int8Array);
// Checking for a view
console.log("Value is a View:",
ArrayBuffer.isView(int8Array));
// Checking for a DataView
isDataView = util.types.isDataView(int8Array);
console.log("Value is a DataView:", isDataView);
// Creating a dataview
let dataView = new DataView(new ArrayBuffer(3));
dataView.setUint8(0, 10);
dataView.setUint8(1, 20);
dataView.setUint8(2, 30);
console.log("Value:", dataView);
// Checking for a view
console.log("Value is a View:",
ArrayBuffer.isView(dataView));
// Checking for a DataView
isDataView = util.types.isDataView(dataView);
console.log("Value is a DataView:", isDataView);
输出:
Value: Uint8Array [ 10, 20, 30 ]
Value is a View: true
Value is a DataView: false
Value: DataView {
byteLength: 3,
byteOffset: 0,
buffer: ArrayBuffer { [Uint8Contents]:
<0a 14 1e>, byteLength: 3 }
}
Value is a View: true
Value is a DataView: true
参考:https://nodejs . org/API/util . html # util _ util _ types _ isdataview _ value
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