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- (window.webpackJsonp=window.webpackJsonp||[]).push([[90],{399:function(s,n,t){"use strict";t.r(n);var a=t(0),e=Object(a.a)({},(function(){var s=this,n=s.$createElement,t=s._self._c||n;return t("ContentSlotsDistributor",{attrs:{"slot-key":s.$parent.slotKey}},[t("h1",{attrs:{id:"instanceof运算符"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#instanceof运算符"}},[s._v("#")]),s._v(" instanceof运算符")]),s._v(" "),t("h4",{attrs:{id:"原文"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#原文"}},[s._v("#")]),s._v(" "),t("a",{attrs:{href:"https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Operators/instanceof",target:"_blank",rel:"noopener noreferrer"}},[s._v("原文"),t("OutboundLink")],1)]),s._v(" "),t("hr"),s._v(" "),t("h2",{attrs:{id:"语法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#语法"}},[s._v("#")]),s._v(" 语法")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("object instanceof constructor\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("blockquote",[t("p",[s._v("参数"),t("br")])]),s._v(" "),t("ol",[t("li",[s._v("object 要检测的对象."),t("br")]),s._v(" "),t("li",[s._v("constructor 某个构造函数")])]),s._v(" "),t("h2",{attrs:{id:"描述"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#描述"}},[s._v("#")]),s._v(" 描述")]),s._v(" "),t("blockquote",[t("p",[s._v("instanceof 运算符用来检测 constructor.prototype 是否存在于参数 object 的原型链上。")])]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("// 定义构造函数\nfunction C(){}\nfunction D(){}\n\nvar o = new C();\n\n// true，因为 Object.getPrototypeOf(o) === C.prototype\no instanceof C;\n\n// false，因为 D.prototype不在o的原型链上\no instanceof D;\n\no instanceof Object; 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// returns false, 检查原型链会找到 undefined\nmyString instanceof String; // returns true\nnewStr instanceof String; // returns true\nmyString instanceof Object; // returns true\n\nmyObj instanceof Object; // returns true, despite an undefined prototype\n({}) instanceof Object; // returns true, 同上\n\nmyString instanceof Date; // returns false\n\nmyDate instanceof Date; // returns true\nmyDate instanceof Object; // returns true\nmyDate instanceof String; // returns false\n')])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br"),t("span",{staticClass:"line-number"},[s._v("15")]),t("br"),t("span",{staticClass:"line-number"},[s._v("16")]),t("br"),t("span",{staticClass:"line-number"},[s._v("17")]),t("br"),t("span",{staticClass:"line-number"},[s._v("18")]),t("br"),t("span",{staticClass:"line-number"},[s._v("19")]),t("br")])]),t("p",[s._v("演示mycar属于Car类型的同时又属于Object类型")]),s._v(" "),t("blockquote",[t("p",[s._v("下面的代码创建了一个类型Car，以及该类型的对象实例mycar. instanceof运算符表明了这个mycar对象既属于Car类型，又属于Object类型。")])]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v('function Car(make, model, year) {\n this.make = make;\n this.model = model;\n this.year = year;\n}\nvar mycar = new Car("Honda", "Accord", 1998);\nvar a = mycar instanceof Car; // 返回 true\nvar b = mycar instanceof Object; // 返回 true\n')])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("h3",{attrs:{id:"instanceof运算符在数组中的使用"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#instanceof运算符在数组中的使用"}},[s._v("#")]),s._v(" instanceof运算符在数组中的使用")]),s._v(" "),t("p",[s._v("确定一个对象在全局中是否为数组")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" colors"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aa'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'bb'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'cc'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//创建包含三个字符串的数组")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("if")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("colors "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("instanceof")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("alert")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("else")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("alert")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//最后输出 1，说明该对象为数组")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])])])}),[],!1,null,null,null);n.default=e.exports}}]);
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