源码阅读 #

var done = function (warnings, errors) {
  var result = {
    validForNewPackages: errors.length === 0 && warnings.length === 0,
    validForOldPackages: errors.length === 0,
    warnings: warnings,
    errors: errors
  }
  if (!result.warnings.length) delete result.warnings
  if (!result.errors.length) delete result.errors
  return result
}

  var warnings = []
  var errors = []

  if (name === null) {
    errors.push('name cannot be null')
    return done(warnings, errors)
  }

'use strict';

var bind = require('./helpers/bind');

// utils is a library of generic helper functions non-specific to axios

var toString = Object.prototype.toString;

/**
 * Determine if a value is an Array
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is an Array, otherwise false
 */
// 通过toString获取对象类型，然后判断是否为数组
function isArray(val) {
  return toString.call(val) === '[object Array]';
}

/**
 * Determine if a value is undefined
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if the value is undefined, otherwise false
 */
// 直接用typeof判断,说起来算是利用了null的缺陷
function isUndefined(val) {
  return typeof val === 'undefined';
}

/**
 * Determine if a value is a Buffer
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is a Buffer, otherwise false
 */
// 先判断是否为null和underfined，然后判断是否存在val构造函数，Buffer本身是个类
// 然后用自己的isBuffer方法判断
function isBuffer(val) {
  return val !== null && !isUndefined(val) && val.constructor !== null && !isUndefined(val.constructor)
    && typeof val.constructor.isBuffer === 'function' && val.constructor.isBuffer(val);
}

/**
 * Determine if a value is an ArrayBuffer
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is an ArrayBuffer, otherwise false
 */
// toString方法直接判断
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
 */
// instanceof 运算符判断 是否是由FormData构造函数创建的对象：当前对象的构造函数是的prototype属性指向的是FormData吗
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;
}

// 简单类型可以直接用typeof判断除了null和undefined
/**
 * 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 an Object
 *
 * @param {Object} val The value to test
 * @returns {boolean} True if value is an Object, otherwise false
 */
// 排除null
function isObject(val) {
  return val !== null && typeof val === 'object';
}

/**
 * Determine if a value is a plain Object
 *
 * @param {Object} val The value to test
 * @return {boolean} True if value is a plain Object, otherwise false
 */
// 判断是否为纯对象，是用系统方法构造的对象 {} 或者 new Object()
function isPlainObject(val) {
  if (toString.call(val) !== '[object Object]') {
    return false;
  }

  var prototype = Object.getPrototypeOf(val);
  return prototype === null || prototype === Object.prototype;
}

/**
 * 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]';
}
// Blob 对象表示一个不可变、原始数据的类文件对象。它的数据可以按文本或二进制的格式进行读取。
// 多用于转码

/**
 * 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
 */
// 一个处理URL查询字符串的对象
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
 */
// 降级使用trim方法
function trim(str) {
  return str.trim ? str.trim() : str.replace(/^\s+|\s+$/g, '');
}

/**
 * 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'
 */
// 判断是否是浏览器环境
function isStandardBrowserEnv() {
  if (typeof navigator !== 'undefined' && (navigator.product === 'ReactNative' ||
                                           navigator.product === 'NativeScript' ||
                                           navigator.product === 'NS')) {
    return false;
  }
  return (
    typeof window !== 'undefined' &&
    typeof document !== 'undefined'
  );
}

/**
 * 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
 */
// Array.foreach的实现
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);
      }
    }
  }
}

/**
 * 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
 */
// 合并多个对象，objec.assign的实现
function merge(/* obj1, obj2, obj3, ... */) {
  var result = {};
  function assignValue(val, key) {
    if (isPlainObject(result[key]) && isPlainObject(val)) {
      result[key] = merge(result[key], val);
    } else if (isPlainObject(val)) {
      result[key] = merge({}, val);
    } else if (isArray(val)) {
      result[key] = val.slice();
    } else {
      result[key] = val;
    }
  }

  for (var i = 0, l = arguments.length; i < l; i++) {
    forEach(arguments[i], assignValue);
  }
  return result;
}

/**
 * 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;
}

/**
 * Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
 *
 * @param {string} content with BOM
 * @return {string} content value without BOM
 */
// 删除UTF-8的BOM，位于文本的开头
function stripBOM(content) {
  if (content.charCodeAt(0) === 0xFEFF) {
    content = content.slice(1);
  }
  return content;
}

module.exports = {
  isArray: isArray,
  isArrayBuffer: isArrayBuffer,
  isBuffer: isBuffer,
  isFormData: isFormData,
  isArrayBufferView: isArrayBufferView,
  isString: isString,
  isNumber: isNumber,
  isObject: isObject,
  isPlainObject: isPlainObject,
  isUndefined: isUndefined,
  isDate: isDate,
  isFile: isFile,
  isBlob: isBlob,
  isFunction: isFunction,
  isStream: isStream,
  isURLSearchParams: isURLSearchParams,
  isStandardBrowserEnv: isStandardBrowserEnv,
  forEach: forEach,
  merge: merge,
  extend: extend,
  trim: trim,
  stripBOM: stripBOM
};