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JavaScript Referensi

JavaScript

JS Tali JS Jumlah JS operator JS laporan JS matematika JS Tanggal JS susunan JS boolean JS RegExp JS Global JS Konversi

Browser BOM

Window Navigator Screen History Location

HTML DOM

DOM Dokumen DOM elemen DOM atribut DOM Acara DOM Gaya

HTML benda

<a> <abbr> <address> <area> <article> <aside> <audio> <b> <base> <bdo> <blockquote> <body> <br> <button> <canvas> <caption> <cite> <code> <col> <colgroup> <datalist> <dd> <del> <details> <dfn> <dialog> <div> <dl> <dt> <em> <embed> <fieldset> <figcaption> <figure> <footer> <form> <head> <header> <h1> - <h6> <hr> <html> <i> <iframe> <img> <ins> <input> button <input> checkbox <input> color <input> date <input> datetime <input> datetime-local <input> email <input> file <input> hidden <input> image <input> month <input> number <input> password <input> radio <input> range <input> reset <input> search <input> submit <input> text <input> time <input> url <input> week <kbd> <keygen> <label> <legend> <li> <link> <map> <mark> <menu> <menuitem> <meta> <meter> <nav> <object> <ol> <optgroup> <option> <output> <p> <param> <pre> <progress> <q> <s> <samp> <script> <section> <select> <small> <source> <span> <strong> <style> <sub> <summary> <sup> <table> <td> <th> <tr> <textarea> <time> <title> <track> <u> <ul> <var> <video>

Objek lainnya

CSSStyleDeclaration

JavaScript undefined Property

<Fungsi JavaScript global

Contoh

Uji jika variabel tidak terdefinisi:

var x;

if (x === undefined) {
txt = "x is undefined";
} else {
txt = "x is defined";
}

Hasil txt akan:

x is undefined

Cobalah sendiri "

Lebih "Try it Yourself" contoh di bawah ini.

Definisi dan Penggunaan

Properti terdefinisi menunjukkan bahwa variabel belum ditetapkan nilai.

Dukungan Browser

Milik
undefined	iya nih	iya nih	iya nih	iya nih	iya nih

Rincian teknis

Versi JavaScript:	1.3

Contoh lebih

Contoh

Uji apakah variabel terdefinisi:

var t1 = "myVar";               // defined
var t2;                         // undefined

if (t1 === undefined) {
    txt1 = "t1 is undefined";
} else {
    txt1 = "t1 is defined";
}

if (t2 === undefined) {
    txt2 = "t2 is undefined";
} else {
    txt2 = "t2 is defined";
}

txt = txt1 + "<br>" + txt2;

Hasil txt akan:

t1 is defined
t2 is undefined

Cobalah sendiri "

<Fungsi JavaScript global