摘要：前言最近在用封裝純數(shù)字的輸入框，開(kāi)發(fā)過(guò)程中發(fā)現(xiàn)不是坑，也有不少值得研究的地方。因此我們能做的是通過(guò)事件作事后補(bǔ)救措施在中攔截輸入法中輸入的和按鍵事件，然后自行出發(fā)事件執(zhí)行補(bǔ)救措施。

?最近在用Polymer封裝純數(shù)字的輸入框，開(kāi)發(fā)過(guò)程中發(fā)現(xiàn)不是坑，也有不少值得研究的地方。本系列打算分4篇來(lái)敘述這段可歌可泣的踩坑經(jīng)歷：

[《動(dòng)手寫(xiě)個(gè)數(shù)字輸入框1：input[type=number]的遺憾》](http://www.cnblogs.com/fsjohn...

《動(dòng)手寫(xiě)個(gè)數(shù)字輸入框2：起手式——攔截非法字符》

《動(dòng)手寫(xiě)個(gè)數(shù)字輸入框3：痛點(diǎn)——輸入法是個(gè)魔鬼》

《動(dòng)手寫(xiě)個(gè)數(shù)字輸入框4：魔鬼在細(xì)節(jié)——打磨光標(biāo)位置》

?辛辛苦苦終于控制只能輸入數(shù)字了，但只要用戶(hù)啟用了輸入法就輕松突破我們的重重包圍:-<心碎得一地都是。這是我們會(huì)想到底有沒(méi)有一個(gè)API可以禁用輸入法呢？答案是有的，但出人意料的是只有IE才支持。

?而其他瀏覽器就呵呵了。。。

?由于chrome、firefox等無(wú)法通過(guò)樣式ime-mode來(lái)處理，因此想到依葫蘆畫(huà)瓢，同樣在keydown事件中對(duì)特定的keyCode進(jìn)行攔截過(guò)濾就好了，誰(shuí)知道在輸入法中按下字符鍵時(shí)keydown事件的keyCode永遠(yuǎn)是229。其規(guī)律為：

按字符鍵時(shí)，keydown中keyCode恒為229，且key為Undefined;而keyup中才會(huì)得到正確的keyCode，且key為正確的字符。

按enter和shift時(shí)僅觸發(fā)keydown不會(huì)觸發(fā)keyup，而keyCode為229。
因此我們能做的是

通過(guò)keyup事件作事后補(bǔ)救措施；

在keydown中攔截輸入法中輸入的enter和shift按鍵事件，然后自行出發(fā)keyup事件執(zhí)行補(bǔ)救措施。
廢話(huà)少講，上代碼！

const keyCode = anyPass(prop("keyCode"), prop("which"))
const isBackspace = eq(8)
        , isDelete = eq(46)
        , isArrowLeft = eq(37)
        , isArrowRight = eq(38)
        , isArrowUp = eq(39)
        , isArrowDown = eq(40)
        , isTab = eq(9)
        , isHome = eq(36)
        , isEnd = eq(35)
const isValidStr = precision =>
                                     a => RegExp("^[+-]?[0-9]*"+ (precision ? "(.[0-9]{0," + precision + "})?" : "") + "$").test(a)

// 獲取min,max,precision值
const lensTarget = lens(a => a.target || a.srcElement)
        , lensMin = lens(a => Number(a.min) || Number(attr(a, "min")) || Number.MIN_SAFE_INTEGER)
        , lensMax = lens(a => Number(a.max) || Number(attr(a, "max")) || Number.MAX_SAFE_INTEGER)
        , lensPrecision = lens(a => Number(a.precision) || Number(attr(a, "precision")) || 0)
        , lensValue = lens(a => a.value, (o, v) => o.value = v)
        , lensDataValue = lens(a => a && a.getAttribute("data-value"), (a, v) => a && a.setAttribute("data-value", v))

const lensTargetMin = lcomp(lensTarget, lensMin)
        , lensTargetMax = lcomp(lensTarget, lensMax)
        , lensTargetPrecision = lcomp(lensTarget, lensPrecision)
        , lensTargetValue = lcomp(lensTarget, lensValue)

const isIME = eq(229)
const isValidChar = c => /[-+0-9.]/.test(c)
const invalid2Empty = c => isValidChar(c) ? c : ""
const recoverValue = v => flatMap(CharSequence(v), invalid2Empty)

// 是否激活I(lǐng)ME
const isInIME = comp(isIME, keyCode)
// 是否為功能鍵
        , isFnKey = comp(anyPass(isArrowLeft, isArrowRight, isArrowUp, isArrowDown, isBackspace, isDelete, isHome, isEnd), keyCode)

$("input[type=text]").addEventListener("keydown", e => {
    var el = view(lensTarget)(e)
        , val = view(lensTargetValue)(e)
    // 暫存value值，keyup時(shí)發(fā)現(xiàn)問(wèn)題可以恢復(fù)出廠設(shè)置
    set(lensDataValue)(el)(val)

    if (isInIME(e)){
        fireKeyup(el)
    }
})
$("input[type=text]").addEventListener("keyup", e => {
    if (isFnKey(e)) return

    var el = view(lensTarget)(e)
        , v = view(lensValue)(el)
        , p = view(lensTargetPrecision)(e)
        , isValid = isValidStr(p)
        , max = view(lensMax)(el)
        , min = view(lensMin)(el)

    var val = recoverValue(v)
    var setVal = set(lensValue)(el)
    if (isValid(val)){
        if (val !== v){
            setVal(val)
        }
        else{
            var n = Number(v)
            if (!gte(max)(n)){
                setVal(max)
            }
            if (!lte(min)(n)){
                setVal(min)
            }
        }
    }
    else{
        setVal(attr(el, "data-value"))
    }
})

// 工具函數(shù)，請(qǐng)無(wú)視我吧:D
const comp =
             (...fns) =>
             (...args) => {
                 let len = fns.length
                 while (len--){
                     args = [fns[len].apply(null, args)]
                 }
                 return args.length > 1 ? args : args[0]
             }
const isSome = x => "undefined" !== typeof x && x !== null
const invokerImpl =
                n =>
                o =>
                m =>
                (...args) => {
                    let args4m = args.splice(0, n)
                        , times = Number(args[0]) || 1
                        , ret = []
                    while (times--){
                        var tmpRet
                        try{
                            tmpRet = o[m].apply(o, args4m)
                        }
                        catch(e){
                            tmpRet = void 0
                        }
                        ret.push(tmpRet)
                    }
                    return ret.length > 1 ? ret : ret[0]
                }
const curry2Partial =
        fn =>
        (...args) => {
                let c = true
                        , i = 0
                        , l = args.length
                        , f = fn
                for (;c && i < l; ++i){
                        c = isSome(args[i])
                        if (c){
                                f = f(args[i])
                        }
                }
                return f
        }
const invoker = curry2Partial(invokerImpl)
const and = (...args) => args.reduce((accu, x) => accu && x, true)
const or = (...args) => args.reduce((accu, x) => accu || x, false)
const allPass = (...fns) => v => fns.reduce((accu, x) => accu && x(v), true)
const anyPass = (...fns) => v => fns.reduce((accu, x) => accu || x(v), false)
const eq = a => b => a === b
const gt = a => b => a > b
const gte = a => anyPass(eq(a), gt(a))
const lt = a => b => a < b
const lte = a => anyPass(eq(a), lt(a))
const prop = k => o => o[k]
const lens = (g, s) => ({getter: g, setter: s})
const lensPath = (...args) => ({ getter: a => args.reduce((accu, x) => accu && accu[x], a) })
const lcomp = (...lenses) => lenses
const view = lenses => a => {
    if (!~Object.prototype.toString.call(lenses).indexOf("Array")){
        lenses = [lenses]
    }
    return lenses.reduce((accu, lens) => accu && lens.getter(accu), a)
}
const set = lenses => a => v => {
    if (!~Object.prototype.toString.call(lenses).indexOf("Array")){
        lenses = [lenses]
    }
    var setLens = lenses.pop()
    var o = view(lenses)(a)
    if (o){
        setLens.setter(o, v)
    }
}

const $ = invoker(1, document, "querySelector")
const attr = (o, a) => invoker(1, o, "getAttribute")(a)
const flatMap = (functor, f) => {
    return functor.flatMap(f)
}
function CharSequence(v){
    if (this instanceof CharSequence);else return new CharSequence(v)
    this.v = v
}
CharSequence.prototype.flatMap = function(f){
    return this.v.split("").map(f).join("")
}

const fireKeyup = (el) => {
    if (KeyboardEvent){
        // DOM3
        var e = new KeyboardEvent("keyup")
        el.dispatchEvent(e)
    }
    else{
        // DOM2
        var e = document.createEvent("KeyboardEvent")
        e.initEvent("keyup", true, true)
        el.dispatchEvent(e)
    }
}

?到這里我們已經(jīng)成功地控制了IME下的輸入，雖然事后補(bǔ)救導(dǎo)致用戶(hù)輸入出現(xiàn)閃爍的現(xiàn)象:D那是不是就over了呢？當(dāng)然不是啦。
用戶(hù)輸入時(shí)，光標(biāo)位置是隨機(jī)的，于是遺留以下問(wèn)題:

在keydow中預(yù)判斷值合法性時(shí)，是假定光標(biāo)位置處于行尾，將導(dǎo)致預(yù)判失誤;

在keyup中對(duì)value重新賦值時(shí)會(huì)導(dǎo)致光標(biāo)移動(dòng)到行尾，嚴(yán)重中斷了用戶(hù)的輸入流程;

type=text會(huì)導(dǎo)致在移動(dòng)端無(wú)法自動(dòng)顯示數(shù)字鍵盤(pán)。

?后面我們會(huì)針對(duì)上述問(wèn)題繼續(xù)探討，敬請(qǐng)留意！
尊重原創(chuàng)，轉(zhuǎn)載請(qǐng)注明來(lái)自：http://www.cnblogs.com/fsjohn... ^_^肥仔John