javascript - How to choose and work with a drop down list in js -


i got problem. created drop down list choosing algorithm work with. works first option not of them. please me?

thanks in advance

var form1 = document.getelementbyid('form1'); var form2 = document.getelementbyid('form2'); var form3 = document.getelementbyid('form3');  var formarray = [];                      formarray.push(form1.innerhtml); formarray.push(form2.innerhtml); formarray.push(form3.innerhtml);  //select drop down list//  function changetocal() {    dropdownlist.selectedindex--;    document.getelementbyid('form').innerhtml = formarray[dropdownlist.selectedindex]; }  //calculate //   document.getelementbyid('form').addeventlistener("submit",      function(event) {         var fieldy = document.getelementbyid('fieldy');         var fieldx = document.getelementbyid('fieldx');         var resultfield = document.getelementbyid('resultfield');          var x = parsefloat(fieldx.value);          var y = parsefloat(fieldy.value);           if(!fieldy.value || !fieldx.value) {         alert("please enter numbers in fields!");         } else if (dropdownlist.selectedindex = 1) {             var result = (y / 100) * x;             resultfield.innertext = "answer: " + result + "."             event.preventdefault();          } else if (dropdownlist.selectedindex = 2) {             var result = (100 / y) * x;             resultfield.innertext = "answer: " + result + "."             event.preventdefault();         } else if (dropdownlist.selectedindex = 3) {             var result = (y / x) * 100;              resultfield.innertext = "answer: " + result + " %."             event.preventdefault();                 } else {             resultfield.innertext = "error"             event.preventdefault();        }          }             );

https://codepen.io/anon/pen/vmznwq

this line:

} else if (dropdownlist.selectedindex = 1) {

needs use comparison equals operator rather assignment equals operator:

} else if (dropdownlist.selectedindex === 1) {

the other if/else clauses incorrect.

i highly recommend using decent ide, highlight potential mistakes you.

you need change this:

dropdownlist.selectedindex--; document.getelementbyid('form').innerhtml = formarray[dropdownlist.selectedindex];

to this:

document.getelementbyid('form').innerhtml = formarray[dropdownlist.selectedindex - 1];

the selectedindex live, if change using -- cause selected value updated.

the way result output assumes there <h3> id resultfield 1 of forms has id set.

other miscellaneous suggestions include...

the id attributes need unique throughout document. have 3 hidden forms , copy around html, leading 4 elements each id (resultfield, fieldx, fieldy). whether document.getelementbyid grabs right 1 down luck.

rather copying around innerhtml of forms you'd better off showing , hiding existing forms using css. alternatively use 1 form , update relevant text match current algorithm.

listening submit event of form seems odd. why not use regular button , listen click event?

if decide keep 3 forms suggest registering separate button handlers each one. fact of code inside big if/else sign need multiple functions rather single function has figure out mode in. code share factored out if appropriate.


Comments

Post a Comment

Popular posts from this blog

angular - Ionic slides - dynamically add slides before and after -

hi i'm using ngfor create set of 3 slides while starting in middle i'm guaranteed able slide left or right on start. when slide right can simple listen reachedend , push slide array i'm looping. but have problem adding slide beginning. if same above , use e.g. array.unshift() or spread add item beginning, view think it's on position 0 , snaps view new slide. the code below work animates slide change index 1. slide = [0,1,2] //example loop slidechanged(event) { if(this.slides.isbeginning()){ this.slide = [this.slide[0]-1, ...this.slide]; this.slides.update(); this.slides.slideto(1) } } <ion-slides [initialslide]="1" (ionslidedidchange)="slidechanged($event)"> <ion-slide *ngfor="let item of slide"> <h1>slide {{item}}</h1> </ion-slide> </ion-slides> any appreciated! you can using ionslidenextend , ionslideprevend events slides . please...
Read more

Add a dynamic header in angular 2 http provider -

i have http interceptor built via tutorial https://scotch.io/@kashyapmukkamala/using-http-interceptor-with-angular2 the problem need have dynamic header changes automatically once changes 'mode' in app. service able tell interceptor change header, or have interceptor pull header (which string)from service each request. able throwing away patch method, call http.patch('new header string') set header string. call in service controls 'mode' setting. wondering if there way interceptor pull recent value service each request or if can add method http provider via interceptor? i've tried call service in interceptor each request returns undefined. because creating new instance of service or copying value before service fired , loaded/changed data. i don't want pass header string every http provider call because defeats purpose of having interceptor, id able set once changes or have provider fetch service before makes request. tl;dr : need add autom...
Read more

minify - Minimizing css files -

i want know how css files can minimized. currently, using external sites css minifier compress css files. however, after removing whitespaces, comments, etc, file sizes reduced 10-15%. how frameworks bootstrap manage make minimized versions kilobytes. as example, css is: body { background-color: #ff0; } the reduction goes 28 bytes 22 bytes other css files have lot more characters still smaller this. actually minifying code means it's remove thing code white space characters new line characters comments block delimiters it reduces amount of code has transferred on web , speed site load fastly.but unreadable format.
Read more