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Simple realization of the synchronous display function of mobile phone number and bank card

This is an interview question from a certain alliance
Isn’t it all about having a clear idea and then optimizing it while writing
At that time, I said that thinking should be calculated The attribute calculates the value of the preview box based on the content of the input box.
Just handle the focus and blur events.
You have to write by hand. I can’t write by hand. Then the interviewer thought that I would be speechless.

Requirements are as follows

The length of the input content in the input box is greater than 0, and the preview information is displayed
Leave the cursor and close the preview information
Insert a special character_ every 4 digits in the preview information, and the input content remains unchanged

Just use the calculated attribute to judge

<template lang="html">
  <p class="zInput">
      <p class="big-show" v-show="showBig">{{txt2}}</p>
      <input type="text"
             @blur="handerBlur"
             @focus="handerFocus"
             v-model="txt">
  </p>
</template>

<script>
export default {
    name: &#39;z-input&#39;,
    data () {
        return {
            txt: &#39;&#39;,
            showBig: false,
        }
    },
    computed: {
        txt2: function () {
            if (this.txt.length > 0) {
                this.showBig = true
            }
            return this.getStr(this.txt, 4)
        }
    },
    methods: {
        handerBlur () {
            this.showBig = false
        },
        handerFocus (evt) {
            if (evt.target.value.length > 0) {
                this.showBig = true
            }
        },
        getStr (str, len) {
            let lenth = str.length
            let len1 = len - 1
            let newStr = &#39;&#39;
            for (var i = 0; i < lenth; i++) {
                if (i % len === len1 && i > 0) {
                    newStr += str.charAt(i) + &#39;_&#39;
                } else {
                    newStr += str.charAt(i)
                }
            }
            if (newStr.length % (len + 1) === 0) {
                // 解决最后一位为补充项问题
                newStr = newStr.substr(0, newStr.length - 1)
            }
            return newStr
        },
    }
}
</script>

<style lang="less">
.zInput{
    position: relative;
    .big-show {
        position: absolute;
        top: -40px;
        font-size: 36px;
        line-height: 40px;
        background-color: red;
    }
}
.zInput{
    top:50px;
}
</style>

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If another length limit is added, the above method is not suitable. The replacement implementation plan
v-model is actually a syntactic sugar
written separately as v-bind:valueandv-on:input

<template lang="html">
  <p class="zInput">
      <p class="big-show" v-show="showBig">{{txt2}}</p>
      <input type="text"
             @blur="handerBlur"
             @focus="handerFocus"
             v-bind:value="txt"
             v-on:input="handerInput">
  </p>
</template>

<script>
export default {
    name: &#39;z-input&#39;,
    data () {
        return {
            txt: &#39;&#39;,
            txt2: &#39;&#39;,
            showBig: false,
        }
    },
    methods: {
        handerInput (evt) {
            let val = evt.target.value.substr(0, 13)
            // 限制长度13位
            this.txt = val
            evt.target.value = val
            if (this.txt.length > 0) {
                this.showBig = true
            }
            this.txt2 = this.getStr(this.txt, 4)
        },
        handerBlur () {
            this.showBig = false
        },
        handerFocus (evt) {
            if (evt.target.value.length > 0) {
                this.showBig = true
            }
        },
        getStr (str, len) {
            let lenth = str.length
            let len1 = len - 1
            let newStr = &#39;&#39;
            for (var i = 0; i < lenth; i++) {
                if (i % len === len1 && i > 0) {
                    newStr += str.charAt(i) + &#39;_&#39;
                } else {
                    newStr += str.charAt(i)
                }
            }
            if (newStr.length % (len + 1) === 0) {
                // 解决最后一位为补充项问题
                newStr = newStr.substr(0, newStr.length - 1)
            }
            return newStr
        },
    }
}
</script>

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Restrict only numbers to be entered
The first thing that comes to mind is to filter out non-numbers when keyup
But The fact is that keydown->handerInput->keyup

is executed first, then it will be processed at keydown , but after keydown modifies evt.target.value, the
evt.target.value obtained in handerInput is still unprocessed, so it is said that in keydownProcessing does not work Must be processed at
handerInput

<input type="text"
       @blur="handerBlur"
       @focus="handerFocus"
       @keyup="handerKeyup"
       @keydown="handerKeydown"
       v-bind:value="txt"
       v-on:input="handerInput">
<script>
       handerKeydown (evt) {
           console.log(&#39;handerKeydown&#39;)
           evt.target.value = evt.target.value.replace(/[^\d]/g, &#39;&#39;)
           // 这里修改不起作用
       },
       handerKeyup (evt) {
           console.log(&#39;keyup&#39;)
           evt.target.value = evt.target.value.replace(/[^\d]/g, &#39;&#39;)
           // 这里执行顺序靠后 修改无用
       },
       handerInput (evt) {
           let val = evt.target.value.substr(0, 13).replace(/[^\d]/g, &#39;&#39;)
           console.log(&#39;handerInput__val&#39;, val)
           //这里拿到的val是纯数字
           evt.target.value = val
           this.txt = val
           if (this.txt.length > 0) {
               this.showBig = true
           }
           this.txt2 = this.getStr(this.txt, 4)
       },
</script>

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Simple implementation of the synchronized display function of mobile phone number and bank card

This is an interview for a certain alliance Question Isn’t it all about having a clear idea and optimizing it while writing
At that time, I mentioned the idea of using calculated properties to calculate the value of the preview box based on the content of the input box
Dealing with focus Just use the blur event
You have to write it by hand, I can’t write it by hand, and then the interviewer thinks I won’t be speechless

Requirements are as follows

Input The data length of the input content in the box is greater than 0, and the preview information is displayed
Leave the cursor and close the preview information
Insert a special character every 4 digits in the preview information Character_, the input content remains unchanged

Just use the calculated attribute to judge

<template lang="html">
  <p class="zInput">
      <p class="big-show" v-show="showBig">{{txt2}}</p>
      <input type="text"
             @blur="handerBlur"
             @focus="handerFocus"
             v-model="txt">
  </p>
</template>

<script>
export default {
    name: &#39;z-input&#39;,
    data () {
        return {
            txt: &#39;&#39;,
            showBig: false,
        }
    },
    computed: {
        txt2: function () {
            if (this.txt.length > 0) {
                this.showBig = true
            }
            return this.getStr(this.txt, 4)
        }
    },
    methods: {
        handerBlur () {
            this.showBig = false
        },
        handerFocus (evt) {
            if (evt.target.value.length > 0) {
                this.showBig = true
            }
        },
        getStr (str, len) {
            let lenth = str.length
            let len1 = len - 1
            let newStr = &#39;&#39;
            for (var i = 0; i < lenth; i++) {
                if (i % len === len1 && i > 0) {
                    newStr += str.charAt(i) + &#39;_&#39;
                } else {
                    newStr += str.charAt(i)
                }
            }
            if (newStr.length % (len + 1) === 0) {
                // 解决最后一位为补充项问题
                newStr = newStr.substr(0, newStr.length - 1)
            }
            return newStr
        },
    }
}
</script>

<style lang="less">
.zInput{
    position: relative;
    .big-show {
        position: absolute;
        top: -40px;
        font-size: 36px;
        line-height: 40px;
        background-color: red;
    }
}
.zInput{
    top:50px;
}
</style>

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If you add a length limit, the above method is not appropriate, change the implementation Solution

v-model is actually a syntactic sugar written separately as
v-bind:value and v-on:input

<template lang="html">
  <p class="zInput">
      <p class="big-show" v-show="showBig">{{txt2}}</p>
      <input type="text"
             @blur="handerBlur"
             @focus="handerFocus"
             v-bind:value="txt"
             v-on:input="handerInput">
  </p>
</template>

<script>
export default {
    name: &#39;z-input&#39;,
    data () {
        return {
            txt: &#39;&#39;,
            txt2: &#39;&#39;,
            showBig: false,
        }
    },
    methods: {
        handerInput (evt) {
            let val = evt.target.value.substr(0, 13)
            // 限制长度13位
            this.txt = val
            evt.target.value = val
            if (this.txt.length > 0) {
                this.showBig = true
            }
            this.txt2 = this.getStr(this.txt, 4)
        },
        handerBlur () {
            this.showBig = false
        },
        handerFocus (evt) {
            if (evt.target.value.length > 0) {
                this.showBig = true
            }
        },
        getStr (str, len) {
            let lenth = str.length
            let len1 = len - 1
            let newStr = &#39;&#39;
            for (var i = 0; i < lenth; i++) {
                if (i % len === len1 && i > 0) {
                    newStr += str.charAt(i) + &#39;_&#39;
                } else {
                    newStr += str.charAt(i)
                }
            }
            if (newStr.length % (len + 1) === 0) {
                // 解决最后一位为补充项问题
                newStr = newStr.substr(0, newStr.length - 1)
            }
            return newStr
        },
    }
}
</script>

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Limit only numbers can be entered

The first thing that comes to mind is to filter out non-digits during
keyupBut the fact is that
keydown-> is executed first handerInput->keyup

Then it will be processed during

keydown, but after keydown changes evt.target.value The
evt.target.value obtained in handerInput is still unprocessed, so processing in keydown does not work must be done in
handerInputTime processing

<input type="text"
       @blur="handerBlur"
       @focus="handerFocus"
       @keyup="handerKeyup"
       @keydown="handerKeydown"
       v-bind:value="txt"
       v-on:input="handerInput">
<script>
       handerKeydown (evt) {
           console.log(&#39;handerKeydown&#39;)
           evt.target.value = evt.target.value.replace(/[^\d]/g, &#39;&#39;)
           // 这里修改不起作用
       },
       handerKeyup (evt) {
           console.log(&#39;keyup&#39;)
           evt.target.value = evt.target.value.replace(/[^\d]/g, &#39;&#39;)
           // 这里执行顺序靠后 修改无用
       },
       handerInput (evt) {
           let val = evt.target.value.substr(0, 13).replace(/[^\d]/g, &#39;&#39;)
           console.log(&#39;handerInput__val&#39;, val)
           //这里拿到的val是纯数字
           evt.target.value = val
           this.txt = val
           if (this.txt.length > 0) {
               this.showBig = true
           }
           this.txt2 = this.getStr(this.txt, 4)
       },
</script>

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