Phenomenon:
When entering the input method 切换到中文, the oninput event will also be triggered during the pinyin process, as follows:
const Demo=()=>{
const [value,setValue]=useState("");
return (
<>
<input onInput={
(e)=>{
console.log("value：",e.target.value)
setValue(e.target.value)
}}/>
<span>{
value}</span>
</>
)
}
One of the problems brought about by this is that the input box may shake during the process of inputting Chinese. How to solve this problem ?
input provides two events, compositionstart and compositionend, refer to the MDN link.
solution:
Optimize the above code
const Demo = () => {
const [value, setValue] = useState("");
return (
<>
<input
onCompositionStart={
(e) => {
console.log("onCompositionStart")
e.target.composing = true
}}
onCompositionEnd={
(e) => {
console.log("onCompositionEnd",e.target.value)
if(!e.target.composing)return;
(e.target.composing = false)
setValue(e.target.value);
}}
onInput={
(e) => {
if(e.target.composing) return;
console.log("value：", e.target.value);
setValue(e.target.value);
}}
/>
<span>{
value}</span>
</>
);
};
This completely solves the problem of the input box when inputting Chinese.
The above solutions actually come from the processing of input box events when the vue source code v-model instructions are implemented.
const directive = {
inserted (el, binding, vnode, oldVnode) {
if (vnode.tag === 'select') {
// #6903
if (oldVnode.elm && !oldVnode.elm._vOptions) {
mergeVNodeHook(vnode, 'postpatch', () => {
directive.componentUpdated(el, binding, vnode)
})
} else {
setSelected(el, binding, vnode.context)
}
el._vOptions = [].map.call(el.options, getValue)
} else if (vnode.tag === 'textarea' || isTextInputType(el.type)) {
el._vModifiers = binding.modifiers
if (!binding.modifiers.lazy) {
el.addEventListener('compositionstart', onCompositionStart)
el.addEventListener('compositionend', onCompositionEnd)
// Safari < 10.2 & UIWebView doesn't fire compositionend when
// switching focus before confirming composition choice
// this also fixes the issue where some browsers e.g. iOS Chrome
// fires "change" instead of "input" on autocomplete.
el.addEventListener('change', onCompositionEnd)
/* istanbul ignore if */
if (isIE9) {
el.vmodel = true
}
}
}
},
function onCompositionStart (e) {
e.target.composing = true
}
function onCompositionEnd (e) {
// prevent triggering an input event for no reason
if (!e.target.composing) return
e.target.composing = false
trigger(e.target, 'input')
}
function trigger (el, type) {
const e = document.createEvent('HTMLEvents')
e.initEvent(type, true, true)
el.dispatchEvent(e)
}
From this we can see how careful squid was when writing the vue framework, and these details were taken into account
Reference link:
Magical use of input box events compositionstart and compositionend