本文实例为大家分享了React Native验证码倒计时工具类的具体代码，供大家参考，具体内容如下

因为以前直接用定时器，没去计算当前的时候，每次退出程序的时候，定时器一直不走，这个工具类简单的解决程序退出后台，定时器不走的bug，那么，直接上代码咯~~

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/**

• Created by zhuang.haipeng on 2017.9.11
• 广告倒计时,验证码倒计时工具类
• 用法: //60 1000 为60秒,60 60 * 100 为60分钟 ...
• let countdownDate = new Date(new Date().getTime() + 60 * 1000)
• CountdownUtil.settimer(countdownDate,(time) => {
• Console.log(time) --> {years: 0,days: 0,hours: 0,min: 0,sec: 49,millisec: 0}
• }
• 切记: 在应用工具类的页面退出的时候,调用CountdownUtil.stop() 清除定时器,以免内存爆了
  */

export default class CountdownUtil {

/* 定时器 /
interval = null;

/**

• 创建定时器

• */
  static settimer(countdownDate,callbak) {
  this.interval = setInterval(() => {
  let time = this.getDateData(countdownDate)
  callbak && callbak(time)
  },1000)
  }

/**

• 侄计时计算 --> 通过此方法计算,可以解决应用退出后台的时候,定时器不走
• @param countdownDate
• @return {}
  /
  static getDateData(countdownDate) {
  let diff = (Date.parse(new Date(countdownDate)) - Date.parse(new Date)) / 1000;

if (diff <= 0) {
 this.stop() // 倒计时为0的时候,将计时器清除
  return 0;
}

const timeLeft = {
  years: 0,sec: 0,millisec: 0,};

if (diff >= (365.25 * 86400)) {
  timeLeft.years = Math.floor(diff / (365.25 * 86400));
  diff -= timeLeft.years * 365.25 * 86400;
}
if (diff >= 86400) {
  timeLeft.days = Math.floor(diff / 86400);
  diff -= timeLeft.days * 86400;
}
if (diff >= 3600) {
  timeLeft.hours = Math.floor(diff / 3600);
  diff -= timeLeft.hours * 3600;
}
if (diff >= 60) {
  timeLeft.min = Math.floor(diff / 60);
  diff -= timeLeft.min * 60;
}
timeLeft.sec = diff;
return timeLeft;

}

/**

• 数字补零 --> 例: 00时01分59秒
• @param num
• @param length
• @return {}
  /
  static leadingZeros(num,length = null) {

let length_ = length;
let num_ = num;
if (length_ === null) {
  length_ = 2;
}
num_ = String(num_);
while (num_.length < length_) {
  num_ = '0' + num_;
}
return num_;

}

/* 清除定时器 /
static stop() {
clearInterval(this.interval);
}
};