onchange创建自动保存功能（javascript）无效

Question

Work by .click to save into localStorage:

    $("check").onclick = function(){
    parkArray = [check1,check2,check3,check4,check5];
    localStorage.removeItem ("saveArray");     
    localStorage.setItem("saveArray",JSON.stringify(parkArray));

Didn't work by onchange to autosave into localstorage

    parkArray = [check1,check2,check3,check4,check5];
    parkArray.onchange = function () {
    localStorage.removeItem ("saveArray");     
    localStorage.setItem("saveArray",JSON.stringify(parkArray));

Can anyone give advise how to solve this if I want Array autosaved when changed? Thank you.

Original link: https://github.com/erictsaiweb/card-parking/blob/master/cardpark.js

Answer 1

You have to work with an callback function.

// initalize
var parkArray = [check1,check2,check3,check4,check5];

// change
changeParkArray([check4,check5,check6,check7,check8], onChangeParkArray);

// change ahain
changeParkArray([check9,check10,check12,check21,check100], onChangeParkArray);


// the function who changes the array
function changeParkArray(newValue, callback){
    parkArray = newValue;
    callback(newValue);
}

// function to run after ParkArray is changed
function onChangeParkArray(data){
    localStorage.removeItem ("saveArray");     
    localStorage.setItem("saveArray",JSON.stringify(data));    
}

Answer 2

You cannot use the function onclick on a jQuery object as it is meant for a JavaScript object (eg document.getElementById('element').onclick.... ) it should be .click or .on('click') .

And you're not targeting your element correctly, check ... Is it a class or an id ...

And onchange does not exist in the array prototype. It's only meant for DOM object like input and select .

What you can do for the array is to check if the array parkArray is the same as the one in localStorage .

eg

$("#check").click(function(){
  var saveArray = (localStorage.saveArray != undefined) ? JSON.parse(localStorage.saveArray) : [];
  parkArray = [check1,check2,check3,check4,check5];

  saveArray.forEach(function(v, i){
    if(parkArray.indexOf(v) < 0){
      localStorage.removeItem ("saveArray");     
      localStorage.setItem("saveArray",JSON.stringify(parkArray));
    }
  });
});