动手写个数字输入框3:痛点——输入法是个魔鬼

前言

 最近在用Polymer封装纯数字的输入框,开发过程中发现不是坑,也有不少值得研究的地方。本系列打算分4篇来叙述这段可歌可泣的踩坑经历:

  1. 《动手写个数字输入框1:input[type=number]的遗憾》
  2. 《动手写个数字输入框2:起手式——拦截非法字符》
  3. 《动手写个数字输入框3:痛点——输入法是个魔鬼》
  4. 《动手写个数字输入框4:魔鬼在细节——打磨光标位置》

IE的先进性

 辛辛苦苦终于控制只能输入数字了,但只要用户启用了输入法就轻松突破我们的重重包围:-<心碎得一地都是。这是我们会想到底有没有一个API可以禁用输入法呢?答案是有的,但出人意料的是只有IE才支持。

<style>
    .disabled-ime-mode{
      /*ime-mode为CSS3规则
         *取值
         *auto: 不影响IME的状态,默认值
         *normal: 正常的IME状态
         *active: 激活本地语言输入法
         *inactive: 激活非本地语言输入法
         *disabled: 禁用IME
         */
        ime-mode: disabled;
    }
</style>

 而其他浏览器就呵呵了。。。

别无他法只能补救~

 由于chrome、firefox等无法通过样式ime-mode来处理,因此想到依葫芦画瓢,同样在keydown事件中对特定的keyCode进行拦截过滤就好了,谁知道在输入法中按下字符键时keydown事件的keyCode永远是229。其规律为:

  1. 按字符键时,keydown中keyCode恒为229,且key为Undefined;而keyup中才会得到正确的keyCode,且key为正确的字符。
  2. entershift时仅触发keydown不会触发keyup,而keyCode为229。
    因此我们能做的是
  3. 通过keyup事件作事后补救措施;
  4. 在keydown中拦截输入法中输入的entershift按键事件,然后自行出发keyup事件执行补救措施。
    废话少讲,上代码!
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)

// 获取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IME
const isInIME = comp(isIME, keyCode)
// 是否为功能键
        , 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)
    // 暂存value值,keyup时发现问题可以恢复出厂设置
    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'))
    }
})

附录:工具函数

// 工具函数,请无视我吧: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)
    }
}

未完待续

 到这里我们已经成功地控制了IME下的输入,虽然事后补救导致用户输入出现闪烁的现象:D那是不是就over了呢?当然不是啦。
用户输入时,光标位置是随机的,于是遗留以下问题:

  1. 在keydow中预判断值合法性时,是假定光标位置处于行尾,将导致预判失误;
  2. 在keyup中对value重新赋值时会导致光标移动到行尾,严重中断了用户的输入流程;
  3. type=text会导致在移动端无法自动显示数字键盘。

总结

 后面我们会针对上述问题继续探讨,敬请留意!
尊重原创,转载请注明来自:/fsjohnhuang/p/6953984.html ^_^肥仔John

posted @ 2017-06-07 09:25 ^_^肥仔John 阅读(...) 评论(...) 编辑 收藏