How to find methods used in your project

Simplify the process by adding plugins as needed and testing differences between moment and dayjs, such as replacing startOf('isoweek') with startOf('week') endOf

JavaScript Code

// Use vscode global RE search to find all places using moment, open in editor and copy the string
const keys = s.match(/(moment\()(.*?)(\)\.)(.*?)(\()/g)

const r1 = keys.map((k) => {
  const p = k
  const reg = new RegExp(/\)\.(.*?)\(/,"g")
  const res = k.match(reg)[0]
  if(res.replace(/\)\.|(|\s+/g,"") === 'set')
  return res.replace(/\)\.|(|\s+/g,"")
})

// console.log(new Set(r1));
/**
Set(25) {
  'add',
  'isAfter',
  'format',
  'diff',
  'endOf',
  'isBefore',
  'subtract',
  'day',
  'unix',
  'toISOString',
  'isBetween',
  'startOf',
  'week',
  'month',
  'valueOf',
  'year',
  'date',
  'fromNow',
  'isSame',
  'weekday',
  'toDate',
  'hour',
  'getTime',
  'set',
  'utcOffset'
}
*/

dayjs without plugins (source code)

Minimal Version

"!function(t,e){"object"==typeof exports&&"undefined"!=typeof module?module.exports=e():"function"==typeof define&&define.amd?define(e):(t="undefined"!=typeof globalThis?globalThis:t||self).dayjs=e()}(this,(function(){"use strict";var t=1e3,e=6e4,n=36e5,r="millisecond",i="second",s="minute",u="hour",a="day",o="week",f="month",h="quarter",c="year",d="date",l="Invalid Date",$=/^(\d{4})[-/]?(\d{1,2})?[-/]?(\d{0,2})[Tt\s]*(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?[.:]?(\d+)?$/,y=/\[([^\]]+)]|Y{1,4}|M{1,4}|D{1,2}|d{1,4}|H{1,2}|h{1,2}|a|A|m{1,2}|s{1,2}|Z{1,2}|SSS/g,M={name:"en",weekdays:"Sunday_Monday_Tuesday_Wednesday_Thursday_Friday_Saturday".split("_"),months:"January_February_March_April_May_June_July_August_September_October_November_December".split("_"),ordinal:function(t){var e=["th","st","nd","rd"],n=t%100;return"["+t+(e[(n-20)%10]||e[n]||e[0])+"]"}},m=function(t,e,n){var r=String(t);return!r||r.length>=e?t:""+Array(e+1-r.length).join(n)+t},v={s:m,z:function(t){var e=-t.utcOffset(),n=Math.abs(e),r=Math.floor(n/60),i=n%60;return(e<=0?"+":"-")+m(r,2,"0")+":"+m(i,2,"0")},m:function t(e,n){if(e.date()<n.date())return-t(n,e);var r=12*(n.year()-e.year())+(n.month()-e.month()),i=e.clone().add(r,f),s=n-i<0,u=e.clone().add(r+(s?-1:1),f);return+(-(r+(n-i)/(s?i-u:u-i))||0)},a:function(t){return t<0?Math.ceil(t)||0:Math.floor(t)},p:function(t){return{M:f,y:c,w:o,d:a,D:d,h:u,m:s,s:i,ms:r,Q:h}[t]||String(t||"").toLowerCase().replace(/s$/,"")},u:function(t){return void 0===t}},g="en",D={};D[g]=M;var p=function(t){return t instanceof _},S=function t(e,n,r){var i;if(!e)return g;if("string"==typeof e){var s=e.toLowerCase();D[s]&&(i=s),n&&(D[s]=n,i=s);var u=e.split("-");if(!i&&u.length>1)return t(u[0])}else{var a=e.name;D[a]=e,i=a}return!r&&i&&(g=i),i||!r&&g},w=function(t,e){if(p(t))return t.clone();var n="object"==typeof e?e:{};return n.date=t,n.args=arguments,new _(n)},O=v;O.l=S,O.i=p,O.w=function(t,e){return w(t,{locale:e.$L,utc:e.$u,x:e.$x,$offset:e.$offset})};var _=function(){function M(t){this.$L=S(t.locale,null,!0),this.parse(t)}var m=M.prototype;return m.parse=function(t){this.$d=function(t){var e=t.date,n=t.utc;if(null===e)return new Date(NaN);if(O.u(e))return new Date;if(e instanceof Date)return new Date(e);if("string"==typeof e&&!/Z$/i.test(e)){var r=e.match($);if(r){var i=r[2]-1||0,s=(r[7]||"0").substring(0,3);return n?new Date(Date.UTC(r[1],i,r[3]||1,r[4]||0,r[5]||0,r[6]||0,s)):new Date(r[1],i,r[3]||1,r[4]||0,r[5]||0,r[6]||0,s)}}return new Date(e)}(t),this.$x=t.x||{},this.init()},m.init=function(){var t=this.$d;this.$y=t.getFullYear(),this.$M=t.getMonth(),this.$D=t.getDate(),this.$W=t.getDay(),this.$H=t.getHours(),this.$m=t.getMinutes(),this.$s=t.getSeconds(),this.$ms=t.getMilliseconds()},m.$utils=function(){return O},m.isValid=function(){return!(this.$d.toString()===l)},m.isSame=function(t,e){var n=w(t);return this.startOf(e)<=n&&n<=this.endOf(e)},m.isAfter=function(t,e){return w(t)<this.startOf(e)},m.isBefore=function(t,e){return this.endOf(e)<w(t)},m.$g=function(t,e,n){return O.u(t)?this[e]:this.set(n,t)},m.unix=function(){return Math.floor(this.valueOf()/1e3)},m.valueOf=function(){return this.$d.getTime()},m.startOf=function(t,e){var n=this,r=!!O.u(e)||e,h=O.p(t),l=function(t,e){var i=O.w(n.$u?Date.UTC(n.$y,e,t):new Date(n.$y,e,t),n);return r?i:i.endOf(a)},$=function(t,e){return O.w(n.toDate()[t].apply(n.toDate("s"),(r?[0,0,0,0]:[23,59,59,999]).slice(e)),n)},y=this.$W,M=this.$M,m=this.$D,v="set"+(this.$u?"UTC":"");switch(h){case c:return r?l(1,0):l(31,11);case f:return r?l(1,M):l(0,M+1);case o:var g=this.$locale().weekStart||0,D=(y<g?y+7:y)-g;return l(r?m-D:m+(6-D),M);case a:case d:return $(v+"Hours",0);case u:return $(v+"Minutes",1);case s:return $(v+"Seconds",2);case i:return $(v+"Milliseconds",3);default:return this.clone()}},m.endOf=function(t){return this.startOf(t,!1)},m.$set=function(t,e){var n,o=O.p(t),h="set"+(this.$u?"UTC":""),l=(n={},n[a]=h+"Date",n[d]=h+"Date",n[f]=h+"Month",n[c]=h+"FullYear",n[u]=h+"Hours",n[s]=h+"Minutes",n[i]=h+"Seconds",n[r]=h+"Milliseconds",n)[o],$=o===a?this.$D+(e-this.$W):e;if(o===f||o===c){var y=this.clone().set(d,1);y.$d[l]($),y.init(),this.$d=y.set(d,Math.min(this.$D,y.daysInMonth())).$d}else l&&this.$d[l]($);return this.init(),this},m.set=function(t,e){return this.clone().$set(t,e)},m.get=function(t){return this[O.p(t)]()},m.add=function(r,h){var d,l=this;r=Number(r);var $=O.p(h),y=function(t){var e=w(l);return O.w(e.date(e.date()+Math.round(t*r)),l)};if($===f)return this.set(f,this.$M+r);if($===c)return this.set(c,this.$y+r);if($===a)return y(1);if($===o)return y(7);var M=(d={},d[s]=e,d[u]=n,d[i]=t,d)[$]||1,m=this.$d.getTime()+r*M;return O.w(m,this)},m.subtract=function(t,e){return this.add(-1*t,e)},m.format=function(t){var e=this,n=this.$locale();if(!this.isValid())return n.invalidDate||l;var r=t||"YYYY-MM-DDTHH:mm:ssZ",i=O.z(this),s=this.$H,u=this.$m,a=this.$M,o=n.weekdays,f=n.months,h=function(t,n,i,s){return t&&(t[n]||t(e,r))||i[n].slice(0,s)},c=function(t){return O.s(s%12||12,t,"0")},d=n.meridiem||function(t,e,n){var r=t<12?"AM":"PM";return n?r.toLowerCase():r},$={YY:String(this.$y).slice(-2),YYYY:this.$y,M:a+1,MM:O.s(a+1,2,"0"),MMM:h(n.monthsShort,a,f,3),MMMM:h(f,a),D:this.$D,DD:O.s(this.$D,2,"0"),d:String(this.$W),dd:h(n.weekdaysMin,this.$W,o,2),ddd:h(n.weekdaysShort,this.$W,o,3),dddd:o[this.$W],H:String(s),HH:O.s(s,2,"0"),h:c(1),hh:c(2),a:d(s,u,!0),A:d(s,u,!1),m:String(u),mm:O.s(u,2,"0"),s:String(this.$s),ss:O.s(this.$s,2,"0"),SSS:O.s(this.$ms,3,"0"),Z:i};return r.replace(y,(function(t,e){return e||$[t]||i.replace(":","")}))},m.utcOffset=function(){return 15*-Math.round(this.$d.getTimezoneOffset()/15)},m.diff=function(r,d,l){var $,y=O.p(d),M=w(r),m=M.utcOffset()-this.utcOffset()*e,v=this-M,g=O.m(this,M);return g=($={},$[c]=g/12,$[f]=g,$[h]=g/3,$[o]=(v-m)/6048e5,$[a]=(v-m)/864e5,$[u]=v/n,$[s]=v/e,$[i]=v/t,$)[y]||v,l?g:O.a(g)},m.daysInMonth=function(){return this.endOf(f).$D},m.$locale=function(){return D[this.$L]},m.locale=function(t,e){if(!t)return this.$L;var n=this.clone(),r=S(t,e,!0);return r&&(n.$L=r),n},m.clone=function(){return O.w(this.$d,this)},m.toDate=function(){return new Date(this.valueOf())},m.toJSON=function(){return this.isValid()?this.toISOString():null},m.toISOString=function(){return this.$d.toISOString()},m.toString=function(){return this.$d.toUTCString()},M}(),T=_.prototype;return w.prototype=T,[["$ms",r],["$s",i],["$m",s],["$H",u],["$W",a],["$M",f],["$y",c],["$D",d]].forEach((function(t){T[t[1]]=function(e){return this.$g(e,t[0],t[1])}})),w.extend=function(t,e){return t.$i||(t(e,_,w),t.$i=!0),w},w.locale=S,w.isDayjs=p,w.unix=function(t){return w(1e3*t)},w.en=D[g],w.Ls=D,w.p={},w}));"

You can call it the ultra-lightweight version

Please note that you will add plugins based on your project requirements

import dayjs from './libs/dayjs/index'
import './libs/dayjs/locale/zh-cn'
// import calendar from './libs/dayjs/plugin/calendar'
// import isBetween from './libs/dayjs/plugin/isBetween'
// import isYesterday from './libs/dayjs/plugin/isYesterday'
// import utc from './libs/dayjs/plugin/utc'
import relativeTime from './libs/dayjs/plugin/relativeTime/index'

// dayjs.extend(calendar)
// dayjs.extend(isBetween)
// dayjs.extend(isYesterday)
dayjs.extend(relativeTime)
dayjs.locale('zh-cn')
export default dayjs
// module.exports = {
//   dayjs
// }