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Two simple components to build a ScrollSpy in React
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import React, { Component, PropTypes, createElement } from 'react' | |
import { findDOMNode } from 'react-dom' | |
// usage: | |
// import { ScrollSpy, Link } = './wherever-this-file-is' | |
// | |
// <ScrollSpy> | |
// <Link ref={c => this._firstLink = c} section="1">Section 1</Link> | |
// <Link section="2">Section 2</Link> | |
// <Link section="3">Section 3</Link> | |
// </ScrollSpy> | |
// <section id="1"> | |
// ... | |
// </section> | |
// <section id="2"> | |
// ... | |
// </section> | |
// <section id="3"> | |
// ... | |
// </section> | |
export class ScrollSpy extends Component { | |
static childContextTypes = { | |
scrollSpy: PropTypes.object | |
} | |
state = { | |
sections: [], | |
currentSection: null | |
} | |
getChildContext() { | |
return { | |
scrollSpy: { | |
registerLink: this._registerLink, | |
currentSection: this.state.currentSection | |
} | |
} | |
} | |
componentDidMount() { | |
this._setCurrentSection() | |
window.addEventListener('scroll', this._setCurrentSection) | |
} | |
componentWillUnmount() { | |
window.removeEventListener('scroll', this._setCurrentSection) | |
} | |
_registerLink = (section) => { | |
const { sections } = this.state | |
sections.push(document.getElementById(section)) | |
this.setState({ sections }) | |
} | |
_setCurrentSection = () => { | |
const { sections } = this.state | |
const sectionCount = sections.length | |
if (!sectionCount) return; | |
let currentSection = this.props.defaultSection ? sections[0].id : null | |
for (let i = 0; i < sectionCount; i++) { | |
const section = sections[i] | |
if (window.pageYOffset > section.offsetTop) { | |
currentSection = section.id | |
} | |
} | |
this.setState({ currentSection }) | |
} | |
render() { | |
return this.props.children | |
} | |
} | |
export class Link extends Component { | |
static contextTypes = { | |
scrollSpy: PropTypes.object | |
} | |
static propTypes = { | |
section: PropTypes.string.isRequired | |
} | |
componentDidMount() { | |
this.context.scrollSpy.registerLink(this.props.section) | |
} | |
render() { | |
const { section, className, children, ...restProps } = this.props | |
const isCurrent = (section === this.context.scrollSpy.currentSection) | |
let classes = className || '' | |
if (typeof children === 'function') { | |
return children(isCurrent) | |
} | |
if (isCurrent) { | |
classes += ' is-current' | |
} | |
return createElement('a', { | |
href: `#${section}`, | |
className: classes, | |
...restProps | |
}, children) | |
} | |
} |
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