<el-input v-model="PJJFform.cpBankZh" @input="cpBankZhFormat()"></el-input>

methods:{
	cpBankZhFormat:function () {
	    this.PJJFform.cpBankZh=this.PJJFform.cpBankZh.replace(/\s/g, '').replace(/[^\d]/g, '').replace(/(\d{4})(?=\d)/g, '$1 ')
    }
}

效果图：

如果在后续接口传参数时，需要把空格去掉，就把对应字段进行如下处理：

this.PJJFform.cpBankZh=this.PJJFform.cpBankZh.trim().replace(/\s/g,"")