angular的format封装

import { Pipe, PipeTransform } from'@angular/core';
@Pipe({
name: 'DatePipe',
pure: true})
exportclassDatePipeimplementsPipeTransform {
private_irregularReg: RegExp=newRegExp('^[\\d]{8}$');
transform(value: string, sepType: string='0', prefix: string='', suffix: string=''): string {
if (value===null||value===''||value===undefined) {
return'';
        } elseif (typeofvalue!=='string') {
returnvalue;
        } elseif (!this._irregularReg.test(value)) {
returnvalue;
        } else {
letfinValue: string='';
if (sepType==='0') {
finValue=value.slice(0, 4) +'/'+value.slice(4, 6) +'/'+value.slice(6, 8);
            } else {
finValue=value.slice(0, 4) +'年'+value.slice(4, 6) +'月'+value.slice(6, 8) +'日';
            }
returnprefix+finValue+suffix;
        }
    }
}