[英]Window is not defined in nextJS
我在 nextJS 項目中收到錯誤“未定義窗口”。 這里 isMobile 存儲窗口大小小於 767.98 或不執行打開/關閉漢堡菜單功能的值。 此代碼在 ReactJS 中運行良好,但在 NextJS 中無法運行。 請幫我弄清楚這個問題。
import Link from 'next/link';
import React, { useState, useEffect, useRef } from "react";
const Navbar = () => {
const isMobile = window.innerWidth <= 767.98;
const [isMenuOpen, setIsMenuOpen] = useState(!isMobile);
const toggle = () => isMobile && setIsMenuOpen(!isMenuOpen);
const ref = useRef()
useEffect(() => {
if (isMobile) {
const checkIfClickedOutside = (e) => {
if (!ref.current?.contains(e.target)) {
setIsMenuOpen(false);
}
};
document.addEventListener("mousedown", checkIfClickedOutside);
return () => {
// Cleanup the event listener
document.removeEventListener("mousedown", checkIfClickedOutside);
};
}
}, []);
return (
<>
<header>
<nav>
<div className="nav">
<div className="nav-brand">
<Link href="/" className="text-black"><a>Website</a></Link>
</div>
<div ref={ref}>
<div className="toggle-icon" onClick={toggle}>
<i id="toggle-button" className={isMenuOpen ? 'fas fa-times' : 'fas fa-bars'} />
</div>
{isMenuOpen && (
<div className={isMenuOpen ? "nav-menu visible" : "nav-menu"}>
<ul className="main-menu">
<li><Link href="/" onClick={toggle}><a>Home</a></Link></li>
<li><Link href="/blog" onClick={toggle}><a>Blog</a></Link></li>
<li className="drp">
<p className="dropbtn">Find <i className="fa-solid fa-angle-down"></i></p>
<ul className="dropdown-content">
<li><Link href="/find/portable-keyboards" onClick={toggle}><a>Portable Keyboards</a></Link></li>
</ul>
</li>
</ul>
</div>
)}
</div>
</div>
</nav>
</header>
</>
)
}
export default Navbar;
Next.js 是一個服務器端渲染框架,這意味着從服務器生成 HTML 的初始調用。 此時, window
對象僅在客戶端可用(不在服務器端)。
要解決此問題,您需要檢查window
對象的可用性。
import Link from 'next/link';
import React, { useState, useEffect, useRef } from "react";
const Navbar = () => {
const isMobile = typeof window !== "undefined" && window.innerWidth <= 767.98
const [isMenuOpen, setIsMenuOpen] = useState(!isMobile);
const toggle = () => isMobile && setIsMenuOpen(!isMenuOpen);
const ref = useRef()
useEffect(() => {
if (isMobile) {
const checkIfClickedOutside = (e) => {
if (!ref.current?.contains(e.target)) {
setIsMenuOpen(false);
}
};
document.addEventListener("mousedown", checkIfClickedOutside);
return () => {
// Cleanup the event listener
document.removeEventListener("mousedown", checkIfClickedOutside);
};
}
}, []);
return (
<>
<header>
<nav>
<div className="nav">
<div className="nav-brand">
<Link href="/" className="text-black"><a>Website</a></Link>
</div>
<div ref={ref}>
<div className="toggle-icon" onClick={toggle}>
<i id="toggle-button" className={isMenuOpen ? 'fas fa-times' : 'fas fa-bars'} />
</div>
{isMenuOpen && (
<div className={isMenuOpen ? "nav-menu visible" : "nav-menu"}>
<ul className="main-menu">
<li><Link href="/" onClick={toggle}><a>Home</a></Link></li>
<li><Link href="/blog" onClick={toggle}><a>Blog</a></Link></li>
<li className="drp">
<p className="dropbtn">Find <i className="fa-solid fa-angle-down"></i></p>
<ul className="dropdown-content">
<li><Link href="/find/portable-keyboards" onClick={toggle}><a>Portable Keyboards</a></Link></li>
</ul>
</li>
</ul>
</div>
)}
</div>
</div>
</nav>
</header>
</>
)
}
export default Navbar;
您可以修復它的另一種方法是您可以將該window
邏輯移動到useEffect
(或基於類的componentDidMount
上的 componentDidMount )
import Link from 'next/link';
import React, { useState, useEffect, useRef } from "react";
const Navbar = () => {
const [isMobile, setIsMobile] = useState(false); //the initial state depends on mobile-first or desktop-first strategy
const [isMenuOpen, setIsMenuOpen] = useState(true);
const toggle = () => isMobile && setIsMenuOpen(!isMenuOpen);
const ref = useRef()
useEffect(() => {
setIsMobile(window.innerWidth <= 767.98)
setIsMenuOpen(window.innerWidth > 767.98)
}, [])
useEffect(() => {
if (isMobile) {
const checkIfClickedOutside = (e) => {
if (!ref.current?.contains(e.target)) {
setIsMenuOpen(false);
}
};
document.addEventListener("mousedown", checkIfClickedOutside);
return () => {
// Cleanup the event listener
document.removeEventListener("mousedown", checkIfClickedOutside);
};
}
}, [isMobile]);
return (
<>
<header>
<nav>
<div className="nav">
<div className="nav-brand">
<Link href="/" className="text-black"><a>Website</a></Link>
</div>
<div ref={ref}>
<div className="toggle-icon" onClick={toggle}>
<i id="toggle-button" className={isMenuOpen ? 'fas fa-times' : 'fas fa-bars'} />
</div>
{isMenuOpen && (
<div className={isMenuOpen ? "nav-menu visible" : "nav-menu"}>
<ul className="main-menu">
<li><Link href="/" onClick={toggle}><a>Home</a></Link></li>
<li><Link href="/blog" onClick={toggle}><a>Blog</a></Link></li>
<li className="drp">
<p className="dropbtn">Find <i className="fa-solid fa-angle-down"></i></p>
<ul className="dropdown-content">
<li><Link href="/find/portable-keyboards" onClick={toggle}><a>Portable Keyboards</a></Link></li>
</ul>
</li>
</ul>
</div>
)}
</div>
</div>
</nav>
</header>
</>
)
}
export default Navbar;
請注意,使用此解決方案,您的 UI 可能會由於isMobile
狀態而出現一些閃爍
您可以在父組件定義上嘗試此操作。
import dynamic from 'next/dynamic'
const Navbar = dynamic(() => import('./Navbar'), { ssr: false });
const Parent = () => {
...
return (
{(typeof window !== 'undefined') &&
<Navbar/>
}
...
<Footer/>
);
}
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