前言
这应该是一个大多数都常用的请求库, 因为它可以支持多种配置, 跨平台实现, 返回 promise 进行链式调用. 完全过一遍源码可以提升自己对请求库的理解知识
什么是 axios？
Axios 是一个基于 promise 的 HTTP 库，可以用在浏览器和 node.js 中
特性
- 从浏览器中创建 XMLHttpRequests
- 从 node.js 创建 http 请求
- 支持 Promise API
- 拦截请求和响应
- 转换请求数据和响应数据
- 取消请求
- 自动转换 JSON 数据
- 客户端支持防御 XSRF
源码目录结构
├── /cancel/ # 定义取消功能实现
│ ├── Cancel.js # 请求被取消后抛出的对象, 构造函数实现
│ ├── isCancel.js # 返回是否已经取消的布尔值
│ └── CancelToken.js # 用来请求取消操作的对象, 构造函数实现
├── /core/ # 主要的核心功能实现
│ ├── Axios.js # axios 的构造函数
│ ├── buildFullPath.js # 返回基础地址和请求地址的合并 URL
│ ├── createError.js # 创建指定错误对象的构造函数
│ ├── dispatchRequest.js # 使用配置的适配器发送请求到服务器
│ ├── enhanceError.js # 修改指定错误对象的信息
│ ├── InterceptorManager.js # 实现拦截器的构造函数
│ ├── mergeConfig.js # 合并配置
│ ├── transformData.js # 转换数据
│ └── settle.js # 根据 http 响应状态，改变 Promise 的状态
├── /helpers/ # 一些辅助方法
│ ├── bind.js # bind 实现方法
│ ├── buildUR.js # URL 末尾追加参数
│ ├── combineURLs.js # 合并 URL
│ ├── cookies.js # cookie 操作
│ ├── deprecatedMethod.js # 警告已废弃请求方式
│ ├── isAbsoluteURL.js # 返回是否绝对路径的布尔值
│ ├── isURLSameOrigin.js # 返回是否同源的布尔值
│ ├── normalizeHeaderName.js # 标准化对比替换请求头
│ ├── parseHeaders.js # 将请求头解析成对象
│ └── spread.js # 用于调用函数和展开参数数组的语法糖
├── /adapters/ # 定义请求的适配器 xhr、http
│ ├── http.js # nodejs 默认适配器
│ └── xhr.js # 浏览器默认适配器
├── axios.js # 默认入口
├── defaults.js # 默认配置
└── utils.js # 工具函数工具函数
这是 axios 的工具函数, 我个人习惯是先看工具函数, 因为这些一般会充斥到整个库, 所以得先有个底知道有什么可以用的工具
axios/lib/utils.js
var bind = require('./helpers/bind');
var isBuffer = require('is-buffer');
/*global toString:true*/
// utils is a library of generic helper functions non-specific to axios
var toString = Object.prototype.toString;引入了上面的 bind 函数和 buffer 检测库, 和对象原型链上的 toString 方法, 我们看看里面的 bind 是怎么样的
axios/lib/helpers/bind.js
module.exports = function bind(fn, thisArg) {return function wrap() {
// 将参数数组化
var args = new Array(arguments.length);
for (var i = 0; i < args.length; i++) {args[i] = arguments[i];
}
return fn.apply(thisArg, args);
};
};bind的简单实现, 没疑问
源码地址
/**
* Determine if a value is an Array
*
* @param {Object} val The value to test
* @returns {boolean} True if value is an Array, otherwise false
*/
function isArray(val) {return toString.call(val) === '[object Array]';
}
/**
* Determine if a value is an ArrayBuffer
*
* @param {Object} val The value to test
* @returns {boolean} True if value is an ArrayBuffer, otherwise false
*/
function isArrayBuffer(val) {return toString.call(val) === '[object ArrayBuffer]';
}
/**
* Determine if a value is a FormData
*
* @param {Object} val The value to test
* @returns {boolean} True if value is an FormData, otherwise false
*/
function isFormData(val) {return (typeof FormData !== 'undefined') && (val instanceof FormData);
}
/**
* Determine if a value is a view on an ArrayBuffer
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a view on an ArrayBuffer, otherwise false
*/
function isArrayBufferView(val) {
var result;
if ((typeof ArrayBuffer !== 'undefined') && (ArrayBuffer.isView)) {result = ArrayBuffer.isView(val);
} else {result = (val) && (val.buffer) && (val.buffer instanceof ArrayBuffer);
}
return result;
}
/**
* Determine if a value is a String
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a String, otherwise false
*/
function isString(val) {return typeof val === 'string';}
/**
* Determine if a value is a Number
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a Number, otherwise false
*/
function isNumber(val) {return typeof val === 'number';}
/**
* Determine if a value is undefined
*
* @param {Object} val The value to test
* @returns {boolean} True if the value is undefined, otherwise false
*/
function isUndefined(val) {return typeof val === 'undefined';}
/**
* Determine if a value is an Object
*
* @param {Object} val The value to test
* @returns {boolean} True if value is an Object, otherwise false
*/
function isObject(val) {return val !== null && typeof val === 'object';}
/**
* Determine if a value is a Date
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a Date, otherwise false
*/
function isDate(val) {return toString.call(val) === '[object Date]';
}
/**
* Determine if a value is a File
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a File, otherwise false
*/
function isFile(val) {return toString.call(val) === '[object File]';
}
/**
* Determine if a value is a Blob
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a Blob, otherwise false
*/
function isBlob(val) {return toString.call(val) === '[object Blob]';
}
/**
* Determine if a value is a Function
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a Function, otherwise false
*/
function isFunction(val) {return toString.call(val) === '[object Function]';
}
/**
* Determine if a value is a Stream
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a Stream, otherwise false
*/
function isStream(val) {return isObject(val) && isFunction(val.pipe);
}
/**
* Determine if a value is a URLSearchParams object
*
* @param {Object} val The value to test
* @returns {boolean} True if value is a URLSearchParams object, otherwise false
*/
function isURLSearchParams(val) {return typeof URLSearchParams !== 'undefined' && val instanceof URLSearchParams;}
/**
* Trim excess whitespace off the beginning and end of a string
*
* @param {String} str The String to trim
* @returns {String} The String freed of excess whitespace
*/
function trim(str) {return str.replace(/^\s*/, '').replace(/\s*$/,'');
}
/**
* Determine if we're running in a standard browser environment
*
* This allows axios to run in a web worker, and react-native.
* Both environments support XMLHttpRequest, but not fully standard globals.
*
* web workers:
* typeof window -> undefined
* typeof document -> undefined
*
* react-native:
* navigator.product -> 'ReactNative'
* nativescript
* navigator.product -> 'NativeScript' or 'NS'
*/
function isStandardBrowserEnv() {
if (typeof navigator !== 'undefined' && (navigator.product === 'ReactNative' ||
navigator.product === 'NativeScript' ||
navigator.product === 'NS')) {return false;}
return (
typeof window !== 'undefined' &&
typeof document !== 'undefined'
);
}都是些利用基础语法的特性检测是否对应的数据类型
/**
* Iterate over an Array or an Object invoking a function for each item.
*
* If `obj` is an Array callback will be called passing
* the value, index, and complete array for each item.
*
* If 'obj' is an Object callback will be called passing
* the value, key, and complete object for each property.
*
* @param {Object|Array} obj The object to iterate
* @param {Function} fn The callback to invoke for each item
*/
function forEach(obj, fn) {
// Don't bother if no value provided
if (obj === null || typeof obj === 'undefined') {return;}
// Force an array if not already something iterable
if (typeof obj !== 'object') {
/*eslint no-param-reassign:0*/
obj = [obj];
}
if (isArray(obj)) {
// Iterate over array values
for (var i = 0, l = obj.length; i < l; i++) {fn.call(null, obj[i], i, obj);
}
} else {
// Iterate over object keys
for (var key in obj) {if (Object.prototype.hasOwnProperty.call(obj, key)) {fn.call(null, obj[key], key, obj);
}
}
}
}校验参数类型分别根据可迭代对象或数组做遍历, 传递每个参数到指定方法执行, 如果参数是对象只会遍历实例本身的属性.
/**
* Accepts varargs expecting each argument to be an object, then
* immutably merges the properties of each object and returns result.
*
* When multiple objects contain the same key the later object in
* the arguments list will take precedence.
*
* Example:
*
* ```js
* var result = merge({foo: 123}, {foo: 456});
* console.log(result.foo); // outputs 456
* ```
*
* @param {Object} obj1 Object to merge
* @returns {Object} Result of all merge properties
*/
function merge(/* obj1, obj2, obj3, ... */) {var result = {};
function assignValue(val, key) {if (typeof result[key] === 'object' && typeof val === 'object') {result[key] = merge(result[key], val);
} else {result[key] = val;
}
}
// 将 result 和当前值做比较
for (var i = 0, l = arguments.length; i < l; i++) {forEach(arguments[i], assignValue);
}
return result;
}接收多个参数对象, 合并所有对象并返回结果, 当多个对象包含相同的 key 时, 后者会覆盖前者. 其中的
forEach(arguments[i], assignValue);
-------------- 等价于 -------------------
for (var key in arguments[i]) {if (Object.prototype.hasOwnProperty.call(arguments[i], key)) {assignValue.call(null, arguments[i][key], key, arguments[i]);
}
}
-------------- 等价于 -------------------
for (var key in arguments[i]) {if (Object.prototype.hasOwnProperty.call(arguments[i], key)) {if (typeof result[key] === 'object' && typeof arguments[i][key] === 'object') {result[key] = merge(result[key], arguments[i][key]);
} else {result[key] = val;
}
}
}利用递归合并每层对象
/**
* Function equal to merge with the difference being that no reference
* to original objects is kept.
*
* @see merge
* @param {Object} obj1 Object to merge
* @returns {Object} Result of all merge properties
*/
function deepMerge(/* obj1, obj2, obj3, ... */) {var result = {};
function assignValue(val, key) {if (typeof result[key] === 'object' && typeof val === 'object') {result[key] = deepMerge(result[key], val);
} else if (typeof val === 'object') {result[key] = deepMerge({}, val);
} else {result[key] = val;
}
}
for (var i = 0, l = arguments.length; i < l; i++) {forEach(arguments[i], assignValue);
}
return result;
}和 merge 相比, 它只有在 typeof result[key] === 'object' && typeof val === 'object' 的时候才会进行合并否则直接赋值, 而 deepMerge 只要 assignValue 的入参为对象则一定合并.
/**
* Extends object a by mutably adding to it the properties of object b.
*
* @param {Object} a The object to be extended
* @param {Object} b The object to copy properties from
* @param {Object} thisArg The object to bind function to
* @return {Object} The resulting value of object a
*/
function extend(a, b, thisArg) {forEach(b, function assignValue(val, key) {if (thisArg && typeof val === 'function') {a[key] = bind(val, thisArg);
} else {a[key] = val;
}
});
return a;
}向某个对象添加另一个对象的属性的扩展函数, 并且指定其中 function 绑定指向
module.exports = {
isArray: isArray,
isArrayBuffer: isArrayBuffer,
isBuffer: isBuffer,
isFormData: isFormData,
isArrayBufferView: isArrayBufferView,
isString: isString,
isNumber: isNumber,
isObject: isObject,
isUndefined: isUndefined,
isDate: isDate,
isFile: isFile,
isBlob: isBlob,
isFunction: isFunction,
isStream: isStream,
isURLSearchParams: isURLSearchParams,
isStandardBrowserEnv: isStandardBrowserEnv,
forEach: forEach,
merge: merge,
deepMerge: deepMerge,
extend: extend,
trim: trim
};以上为当前源码导出的所有工具函数
源码地址