Vue.js source code defines some tool methods, browser side, server side vue.js can share these methods

Vue 2.x

Based on the 2.6.14

  • Specific path: SRC \shared\util.js

  • Background: Build a type system based on flow

  • Objective: To help program generate better VM code in JS engine, conducive to performance optimization, improve efficiency

Type judgment

isUndef & isDef

Check whether the value is undefined or null

function isUndef (v) {
  return v === undefined || v === null
}
function isDef (v) {
  returnv ! = =undefined&& v ! = =null
}
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isTrue & isFalse

Determine whether it is true or false

function isTrue (v) {
  return v === true
}
function isFalse (v) {
  return v === false
}
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isPrimitive

Whether the data type is a base type (partial)

function isPrimitive (value) {
  return (
    typeof value === 'string' ||
    typeof value === 'number' ||
    typeof value === 'symbol' ||
    typeof value === 'boolean')}Copy the code

Eg: SRC \core\vdom\create-element.js createElement

 if (Array.isArray(data) || isPrimitive(data)) {/ /... }
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isObject

Whether it is a reference type or a type constructed by new

This method is used in Vue for quick object checking: to identify an object from a known value when that value is of a type that conforms to JSON

function isObject (obj) {
  returnobj ! = =null && typeof obj === 'object'  // Note that null is in the typeof pit
}
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isPromise

Is it a Promise function

function isPromise (val) {
  return (
    isDef(val) &&
    typeof val.then === 'function' &&
    typeof val.catch === 'function')}Copy the code

Eg: SRC \core\util\error. Js invokeWithErrorHandling for handling asynchronous exceptions

if(res && ! res._isVue && isPromise(res) && ! res._handled) {/ /... }
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toRawType

Gets the string of the original type of the value

Based on the Object. The prototype. ToString. Call, in addition to the custom types, almost universal. Return: ‘[object, type]

var _toString = Object.prototype.toString;

function toRawType (value) {
    return _toString.call(value).slice(8, -1)}Copy the code

Eg: SRC \core\util\options.js normalizeProps, normalizing the props property

// The props property type does not meet the requirements
warn(
    `Invalid value for option "props": expected an Array or an Object, ` +
    `but got ${toRawType(props)}. `,
    vm
) 
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hasOwnProperty

Checks whether the object has the specified attribute

var hasOwnProperty = Object.prototype.hasOwnProperty;
function hasOwn (obj, key) {
  return hasOwnProperty.call(obj, key)
}
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Data conversion

toNumber

Convert to numbers

// Convert the value to a number. If the conversion fails, return the original string
function toNumber (val) {
  var n = parseFloat(val);
  return isNaN(n) ? val : n
}
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toString

Convert to string

function toString (val) {
  return val == null
    ? ' '
    : Array.isArray(val) || (isPlainObject(val) && val.toString === _toString)
      ? JSON.stringify(val, null.2)  // For arrays or objects
      : String(val)
}
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Json.stringify (value[, replacer [, space]]);

toArray

Convert an array-like object to an array

function toArray (list, start) {
  start = start || 0;
  var i = list.length - start;
  var ret = new Array(i);
  while (i--) {
    ret[i] = list[i + start];
  }
  return ret
}
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Eg: SRC \core\global-api\use.js initUse

 const args = toArray(arguments.1) // arguments can understand the array object of the arguments passed to the function
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To convert an array-like object to an array, use the following methods:

(1) Array. The prototype. Slice. The call

(2) Array. The from ()

toObject

Merges an array of objects into an object

// Assign attributes to the target object
function extend (to, _from) {
  for (var key in _from) {
    to[key] = _from[key];
  }
  return to
}

function toObject (arr) {
  var res = {};
  for (var i = 0; i < arr.length; i++) {
    if(arr[i]) { extend(res, arr[i]); }}return res
}
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Eg: SRC \platforms\weex\ Runtime \modules\style.js updateStyle

if (Array.isArray(style)) {
    style = vnode.data.style = toObject(style)
}
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It is known that v-bind:style’s array syntax can apply multiple style objects to the same element

capitalize

Uppercase

// cached method below
var capitalize = cached(function (str) {
  return str.charAt(0).toUpperCase() + str.slice(1)});Copy the code

hyphenate

Camelback shortened horizontal line separation

var hyphenateRE = /\B([A-Z])/g;
var hyphenate = cached(function (str) {
  return str.replace(hyphenateRE, '- $1').toLowerCase()
});
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camelize

The short horizontal line is changed to hump

var camelizeRE = /-(\w)/g;
var camelize = cached(function (str) {
  return str.replace(camelizeRE, function (_, c) { return c ? c.toUpperCase() : ' '; })});Copy the code

Cache data

cached

The pass is a function and the return is a function that is used to cache the function created. The capitalize, hyphenate, and capitalize described above all use the cached method

Why do you do that? Especially great ingenuity: conducive to performance optimization.

For details: Portal 1 Portal 2

function cached (fn) {
  var cache = Object.create(null);
  return (function cachedFn (str) {
    var hit = cache[str];  // Cache
    return hit || (cache[str] = fn(str))
  })
}
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makeMap

Define a set of data that can be used to determine whether or not it is a built-in HTML tag

/ * * *@description: 
 * @param STR The character string *@param ExpectsLowerCase whether lowercase * is required@return {*}* /
function makeMap (str, expectsLowerCase) {
  var map = Object.create(null);
  var list = str.split(', ');
  for (var i = 0; i < list.length; i++) {
    map[list[i]] = true;
  }
  return expectsLowerCase
    ? function (val) { return map[val.toLowerCase()]; }
    : function (val) { returnmap[val]; }}Copy the code

Eg: SRC \platforms\web\util\element.js isHTMLTag

var isHTMLTag = makeMap(
  'html,body,base,head,link,meta,style,title,' +
  '... ' +
  'content,element,shadow,template,blockquote,iframe,tfoot'
)

isHTMLTag('iframe')   // true
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Determines whether objects are equal

looseEqual

The overall idea: first type judgment, and then recursive call

function looseEqual (a, b) {
  // a, b are equal to, return true
  if (a === b) { return true }
  var isObjectA = isObject(a);
  var isObjectB = isObject(b);
  // Determine if it is an object (reference type)
  if (isObjectA && isObjectB) {
    try {
      var isArrayA = Array.isArray(a);
      var isArrayB = Array.isArray(b);
      if (isArrayA && isArrayB) {
        If the length of each item is the same, return false if the length is not the same
        return a.length === b.length && a.every(function (e, i) {
          return looseEqual(e, b[i])
        })
      } else if (a instanceof Date && b instanceof Date) {
        // If the two types are Date, use the timestamp to check
        return a.getTime() === b.getTime()
      } else if(! isArrayA && ! isArrayB) {If the length of each attribute is the same, return false if the length is not the same
        var keysA = Object.keys(a);
        var keysB = Object.keys(b);
        return keysA.length === keysB.length && keysA.every(function (key) {
          return looseEqual(a[key], b[key])
        })
      } else {
        /* istanbul ignore next */
        return false}}catch (e) {
      /* istanbul ignore next */
      return false}}else if(! isObjectA && ! isObjectB) {// If neither is an object (reference type), convert it to a string comparison
    return String(a) === String(b)
  } else {
    return false}}Copy the code

other

remove

Delete an array item

function remove (arr, item) {
  if (arr.length) {
    var index = arr.indexOf(item);
    if (index > -1) {
      return arr.splice(index, 1)}}}Copy the code

once

The function is executed only once

function once (fn) {
  var called = false;
  return function () {
    if(! called) { called =true;
      fn.apply(this.arguments); }}}Copy the code

Vue 3.x

Based on the 3.2.6

  • Source link

  • Background: Type validation is based on TypeScript, and instead of flow, we have to mention Vue2. X’s compelling comments

// src\core\instance\lifecycle.js
const propOptions: any = vm.$options.props // wtf flow?

// src\platforms\web\server\modules\dom-props.js
// $flow-disable-line (WTF?)
const attr = propsToAttrMap[key] || key.toLowerCase()
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TypeScript vs Flow, what a nice follow-up to TypeScript. Portals

Reserve & Supplement

  • CacheStringFunction: Reserved, that is, cached

  • MakeMap: keep

  • LooseEqual: Retain, rewrite optimization, supplement looseCompareArrays method, compare whether two arrays are equal or not

// source code: packages shared SRC looseequal.ts
function looseCompareArrays(a, b) {
    // If the length is inconsistent, return false
    if(a.length ! == b.length)return false;
    let equal = true;
    // If the length is the same, compare each item
    for (let i = 0; equal && i < a.length; i++) {
        equal = looseEqual(a[i], b[i]);
    }
    return equal;
}
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  • Data conversion

    • Remove toArray and toObject

      The toArray with Array. Prototype. Slice. Call and Array from instead

    • Added toTypeString, object to string

    const objectToString = Object.prototype.toString;
const toTypeString = (value) = > objectToString.call(value);

toTypeString({num: 0})  // "[object Object]"
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  • Type judgment: supplementary adjustment, more detailed

const isArray = Array.isArray;
const isMap = (val) = > toTypeString(val) === '[object Map]';
const isSet = (val) = > toTypeString(val) === '[object Set]';
const isDate = (val) = > val instanceof Date;
const isFunction = (val) = > typeof val === 'function';
const isString = (val) = > typeof val === 'string';
const isSymbol = (val) = > typeof val === 'symbol';
const isObject = (val) = >val ! = =null && typeof val === 'object';
const isPromise = (val) = > {
    return isObject(val) && isFunction(val.then) && isFunction(val.catch);
};
/ /...
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new

getGlobalThis

Gets the global this to the object

let _globalThis;
const getGlobalThis = () = > {
    // If _globalThis is already defined (executed method), it is returned without further judgment
    return (_globalThis ||
        (_globalThis =
            typeofglobalThis ! = ='undefined'
                ? globalThis
                : typeofself ! = ='undefined'
                    ? self
                    : typeof window! = ='undefined'
                        ? window
                        : typeof global! = ='undefined'
                            ? global
                            : {}));
};
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def

Defining object properties

const def = (obj, key, value) = > {
    Object.defineProperty(obj, key, {
        configurable: true.// It is configurable
        enumerable: false.// not enumerable
        value
    });
};
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isModelListener

Checks whether the current string starts with onUpdate:

const isModelListener = (key) = > key.startsWith('onUpdate:');
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String. The prototype. The startsWith (searchString [position]) : returns a Boolean value that indicates whether the parameter String in the head of the original String.

isIntegerKey

Checks whether the value is an integer key

const isIntegerKey = (key) = >isString(key) && key ! = ='NaN' &&
    key[0]! = =The '-' &&
    ' ' + parseInt(key, 10) === key;
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invokeArrayFns

FNS is an array, each element is a function, traversal number group execution, facilitate the execution of multiple functions at one time

const invokeArrayFns = (fns, arg) = > {
    for (let i = 0; i < fns.length; i++) { fns[i](arg); }};Copy the code

hasChanged

Comparing two values for equality, using object. is, behaves essentially the same as the strict comparison operator (===), but note:

  • Plus 0 is not equal to minus 0
  • NaN equals itself
const hasChanged = (value, oldValue) = > !Object.is(value, oldValue);

hasChanged(+0, -0)  // true
hasChanged(NaN.NaN) // false
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Link drive door

JSON.stringify

Class is bound to Style

Object.is

Last but not least

If there is anything wrong, please give me your advice