JavaScript makes a drop-down list of provincial and municipal cascading



The Object.options.add (new option Label,value) method adds an option object to the collection; The Object.options.remove (index) method removes the specified item from the options collection; Object.options (index) or Options.item (index) can get the specified item of the options collection by index; The select tag also has a property of SelectedIndex, which may get the currently selected option index: Object.selectedindex 1. Clear the Options collection function Optionsclear (object) {var length = Object.options.length;for (var i=length-1;i>=0;i--) { E.options.remove (i);}} 2. Add a new Optionfunction AddOption (object) {Object.add (new Option (Label,value));// Use the last item in the options collection to get focus Object.selectedindex = object.lentht-1;} 3. Delete an item specified in the Options collection Optionfunction removeoption (index) {if (index >= 0) {object.remove (index);// Use the last item in the options collection to get focus Object.selectedindex = Object.lentht-1;}} 4. Gets the real value of the currently selected option Valuefunction Getcurrentoptionvalue (index) {if (index >= 0) return Object (index). value; 5. Gets the display value of the currently selected option Labelfunction Getcurrentoptionlabel (index) {if (index >= 0) return Object (index). text; The following is the date linkage drop-down box: function YYYYMMDD () {//sets the set of months Monhead = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];//all contents of the purge year drop-down box, most notably The space var yobj = document.form1.yearoptionsClear (yobj);//give the under decade frame the content yObj.options.add ("select", 0)); for (var i = 1950; I <= new Date (). getFullYear (); i++)//On a 1950-year basis, to the end of this year Document.form1.year.options.add (new Option (I, I);//Clears all contents of the Month drop-down box, most notably the space var mobj = document.form1.month;optionsclear (mobj);// Re-assign the month drop-down box document.form1.month.options.add (New option ("select", 0)); for (var i = 1; i <; i++) Document.form1.month.options.add (New Option (i,i));//assigns the year's initial value Document.form1.year.value = Document.getelementsbyname ("YYYY") [0].value;//assigns the month's initial value Document.form1.month.value = Document.getelementsbyname ("MM") [0].value;//date dropdown box var n = monhead[ Document.form1.month.value-1];if (Document.form1.month.value ==2 && ispinyear (yyyyvalue)) N++;writeday (n); /assignment of the initial value of the date Document.form1.date.value = Document.getelementsbyname ("DD") [0].value;} Changes in the date of the year (mainly to judge the leap common year) function Yyyydd (str) {var mmvalue = document.form1.month.options[ Document.form1.month.selectedindex].value;if (Mmvalue = = "") {var e = document.form1.date;optionsclear (e); return;} var n = monhead[mmvalue-1];if (Mmvalue = = 2 && ispinyear (str)) N++;writeday (n)}//Month Change Date linkage function MMDD (str) {V Ar yyyyvalue = Document.form1.year.options[document.form1.year.selectedindeX].value;if (Yyyyvalue = = "") {var e = document.form1.date;optionsclear (e); return;} var n = monhead[str-1];if (str = = 2 && ispinyear (yyyyvalue)) N++;writeday (n)}//the drop-down box function Writeday (n) {v) according to the conditional write date Ar e = document.form1.date;optionsclear (e), for (Var I=1; i< (n+1); i++) E.options.add (new Option (I,i));} Determine if leap common year function ispinyear (year) {return (0 = = year%4 && (year0!=0 | | [email protected] = = 0);} Clears all contents of the drop-down box function Optionsclear (e) {var length = Object.options.length;for (var i=length-1;i>=0;i--) { E.options.remove (i);}} and send some perks. 1 Check if checked if (Objselect.selectedindex >-1) {//description checked} else {//description not checked}//2 Delete selected item OBJSELECT.OPTIONS[OBJSELECT.SELECTE Dindex] = null;//3 add objselect.options[objselect.length] = new option ("Hello", "Hello");//4 modify the item in the selection objselect.option S[objselect.selectedindex] = new option ("Hi", "Hello");//5 gets the text of the selected item Objselect.options[objselect.selectedindex].text ;//6 gets the value of the selected item Objselect.options[objselect.selectedindex].value;

JavaScript makes a drop-down list of provincial and municipal cascading