initGlobalAPI

很多小伙伴可能都不太清楚Vue函数自带了很多属性与方法，这些属性与方法在我们平时书写代码的时候都有非常重要的作用

  function initGlobalAPI (Vue) {
    // config
    var configDef = {};
    configDef.get = function () { return config; };
    {
      configDef.set = function () {
        warn(
          'Do not replace the Vue.config object, set individual fields instead.'
        );
      };
    }
    Object.defineProperty(Vue, 'config', configDef);

    // exposed util methods.
    // NOTE: these are not considered part of the public API - avoid relying on
    // them unless you are aware of the risk.
    Vue.util = {
      warn: warn,
      extend: extend,
      mergeOptions: mergeOptions,
      defineReactive: defineReactive$$1
    };

    Vue.set = set;
    Vue.delete = del;
    Vue.nextTick = nextTick;

    // 2.6 explicit observable API
    Vue.observable = function (obj) {
      observe(obj);
      return obj
    };

    Vue.options = Object.create(null);
    ASSET_TYPES.forEach(function (type) {
      Vue.options[type + 's'] = Object.create(null);
    });

    // this is used to identify the "base" constructor to extend all plain-object
    // components with in Weex's multi-instance scenarios.
    Vue.options._base = Vue;

    extend(Vue.options.components, builtInComponents);

    initUse(Vue);
    initMixin$1(Vue);
    initExtend(Vue);
    initAssetRegisters(Vue);
  }

config

  var config = ({
    /**
     * Option merge strategies (used in core/util/options)
     */
    // $flow-disable-line
    optionMergeStrategies: Object.create(null),

    /**
     * Whether to suppress warnings.
     */
    silent: false,

    /**
     * Show production mode tip message on boot?
     */
    productionTip: "development" !== 'production',

    /**
     * Whether to enable devtools
     */
    devtools: "development" !== 'production',

    /**
     * Whether to record perf
     */
    performance: false,

    /**
     * Error handler for watcher errors
     */
    errorHandler: null,

    /**
     * Warn handler for watcher warns
     */
    warnHandler: null,

    /**
     * Ignore certain custom elements
     */
    ignoredElements: [],

    /**
     * Custom user key aliases for v-on
     */
    // $flow-disable-line
    keyCodes: Object.create(null),

    /**
     * Check if a tag is reserved so that it cannot be registered as a
     * component. This is platform-dependent and may be overwritten.
     */
    isReservedTag: no,

    /**
     * Check if an attribute is reserved so that it cannot be used as a component
     * prop. This is platform-dependent and may be overwritten.
     */
    isReservedAttr: no,

    /**
     * Check if a tag is an unknown element.
     * Platform-dependent.
     */
    isUnknownElement: no,

    /**
     * Get the namespace of an element
     */
    getTagNamespace: noop,

    /**
     * Parse the real tag name for the specific platform.
     */
    parsePlatformTagName: identity,

    /**
     * Check if an attribute must be bound using property, e.g. value
     * Platform-dependent.
     */
    mustUseProp: no,

    /**
     * Perform updates asynchronously. Intended to be used by Vue Test Utils
     * This will significantly reduce performance if set to false.
     */
    async: true,

    /**
     * Exposed for legacy reasons
     */
    _lifecycleHooks: LIFECYCLE_HOOKS
  });

以上配置中主要的是以下几点:

optionMergeStrategies

用于定义data,prop,created...等等属性的函数,例如我们Vue传入一个data属性，它并不是一个简单获取的过程，而是通过该属性下的定义的函数进行获取的(在接下来我们会说到这个)

_lifecycleHooks

顾名思义 - 生命周期集合(内部还具有errorCaptrued等等，在接下来我们会说到它的作用到底是什么？)

util

  Vue.util = {
    warn: warn,
    extend: extend,
    mergeOptions: mergeOptions,
    defineReactive: defineReactive$$1
  };

extend

  function extend(to, _from) {
    for (let key in _form) {
      to[key] = _from[key]
    }

    return to
  }

作用: 将第二个参数赋值给第一个参数

以下涉及的模块不同

以下这些都是会分布在各个模块里会去说到，这里就不详细介绍了

set

del

nextTick

observable

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