我怎樣才能調用函數一次點擊JavaScript它只運行一次

Question

<script> 
var myValue = parseInt(12); 
function fontresize(value){ 
var getval = parseInt(value); 
var chngeval = myValue + getval; 
localStorage.setItem("fontset", chngeval); 
    document.getElementById("changefont").style.fontSize = chngeval + "px"; 
} 

window.onload = function(){ 
    var allstorage = localStorage.fontset; 

    if(allstorage != undefined || allstorage == ""){ 
    document.getElementById("changefont").style.fontSize = allstorage + "px"; 
    } 

}; 

<button onClick="fontresize('5')">+</button> 

在是增加我的網頁字體大小的代碼，但問題是它只運行一次當頁面加載我想調用一個函數每一次點擊都可以用java腳本來完成。

Answer 1

你不更新的myValue函數內部的值，所以每當單擊該按鈕，計算字體大小將總是是12 + 5。

更新您fontresize如下：

function fontresize(value) 
{ 
    var getval = parseInt(value), 
     chngeval = myValue = (myValue + getval); 

    localStorage.setItem("fontset", chngeval); 
    document.getElementById("changefont").style.fontSize = chngeval + "px"; 
} 

jsFiddle Demo

---

順便說一句，你的第一個行parseInt()是多餘的; 12已經是整數，那麼你可以使用：

var myValue = 12; 

Answer 2

Plunker

var fontSize = 0; 
document.getElementById('btn').addEventListener('click', function() { 
    fontresize(fontSize+=5); 
}); 

Answer 3

嘗試移動chngeval外fontresize，使用+=操作遞增chngeval;還以localStorage

var myValue = 12, chngeval = 0; 

function fontresize(value) { 
    var getval = parseInt(value); 
    chngeval += myValue + getval; 
    localStorage.setItem("fontset", chngeval); 
    console.log(localStorage.getItem("fontset")) 
    document.getElementById("changefont").style.fontSize = chngeval + "px"; 
} 

window.onload = function() { 
    var allstorage = localStorage.fontset; 

    if (allstorage !== null || allstorage === "") { 
    document.getElementById("changefont").style.fontSize = allstorage + "px"; 
    } 

}; 

plnkr http://plnkr.co/edit/9eSDtDEvUxhPjqa2h0Z0?p=preview