How to send HTML form values to localstorage in JSON string using JavaScript

Question

what is the easiest way to retrieve form values to send to localStorage as a JSON string? I started a function with a for loop but am stuck..any nudges are greatly appreciated(still very new to this) No JQuery please. Thank you

 <input type="submit" name="submit" value="submitOrder" onclick="return getValues();">

var userOrder='';
function getValues(){
    for(var i=0; i < document.forms[0].length - 1; i++){
        console.log(document.forms[0][i]);
        return false;
    }
}    

localStorage.setItem('userOrder',JSON.stringify(userOrder));
console.log(localStorage.getItem('userOrder'));

Answer 1

No need for jQuery. This uses ES 2015 syntax but if you need to support old browsers just run it through babel.

// Iterate over all the forms in the document as an array,
// the [...stuff] turns the nodelist into a real array
let userdata = [...document.forms].map(form => {
  // iterate over all the relevant elements in the form and
  // create key/value pairs for the name/object
  return [...form.elements].reduce((obj, el) => {
    // Every form control should have a name attribute
    obj[el.name] = el.value;
    return obj;
  }, {});
});

// convert the data object to a JSON string and store it
localStorage.setItem('userOrder', JSON.stringify(userdata));

// pull it pack out and parse it back into an object
let data = JSON.parse(localStorage.getItem('userOrder'));

If the forms all have ids (and they should) you could also use reduce in the outer layer instead of map and hash on the form id:

let userdata = [...document.forms].reduce((result, frm) => {
  result[frm.id] = [...frm.elements].reduce((obj, el) => {

and so on.

Answer 2

You could do it like this:

html:

<form id="myform">
  <input type="text" name="test">
  <input type="submit" value="submitOrder">
</form>

js:

const userOrder = {};

function getValues(e) {
  // turn form elements object into an array
  const elements = Array.prototype.slice.call(e.target.elements);

  // go over the array storing input name & value pairs
  elements.forEach((el) => {
    if (el.type !== "submit") {
      userOrder[el.name] = el.value;
    }
  });

  // finally save to localStorage
  localStorage.setItem('userOrder', JSON.stringify(userOrder));
}  

document.getElementById("myform").addEventListener("submit", getValues);