JavaScript:检查cookie是否设置，并在刷新时将图像src更改为随机，cookie不会过期

Question

对不起，标题太长了。我试图做一些简单的事情，加载时运行的函数，检查是否设置了cookie-如果"它是真的"，然后随机更改图像src，如下所示：

HTML代码：

<img id="photo" src="../photostock/3129_382a101ee6d307dfd34abad8941c35cd_8885.jpg" alt="background" />

JS代码：

function rand_photo( id ) {
var q, img, id;
var random = function(min, max) {
return Math.Floor( Math.random() * ( max - min + 1 ) ) + min;
};
q = random( 1, 3 );
var prefix = '../photostock/',
suffix = '.jpg';
switch( q ) {
case 1: 
img = '3129_382a101ee6d307dfd34abad8941c35cd_8885';
break;
case 2: 
img = '1404_0d03ec48b64b4b65a6820aa5a58a39af_5487';
break;
case 3: 
img = '1292_5d3c0fde3f83d725eb58025a522a6097_5648';
break;
default:
img = '7395_5d3c0fde3f83d725eb58025a522a6097_4191';
}
img = prefix + img + suffix;
document.getElementById( id ).setAttribute( 'src' ) = img;
// also tried with just ".src =" - didn't worked
}
function check_create_cookie( cookie_name, ident ) {
if( document.cookie.indexOf( cookie_name ) >= 0 ) {
rand_photo( ident )
}
else {
document.cookie = cookie_name + '=1; max-age=60';
}
}
window.onload = check_create_cookie( 'sample_cookie', 'photo' );

但由于某种原因，它不起作用。。。有什么想法、笔记或两者兼而有之？

谢谢大家！

Answer 1

window.onload = check_create_cookie( 'sample_cookie', 'photo' );

此赋值函数的结果不是函数。正确的语法是

window.onload = function(){check_create_cookie( 'sample_cookie', 'photo' );};

Answer 2

您的代码中有一些拼写错误。

1. Math.Floor不存在：正确的形式是：Math.Floor
2. document.getElementById(id).setAttribute('src')=img；是错误的。正确的格式是：document.getElementById(id).setAttribute('src'，img)；有关详细信息，请参阅MDN
3. 最后一个是：window.onload=check_create_cookie('sample_cookie'，'photo')；正确的形式在MDN中有很好的描述

因此，工作代码为：

function rand_photo(id) {
var q, img, id;
var random = function(min, max) {
return Math.floor(Math.random() * ( max - min + 1 ) ) + min;
};
q = random( 1, 3 );
var prefix = '../photostock/',
suffix = '.jpg';
switch( q ) {
case 1:
img = '3129_382a101ee6d307dfd34abad8941c35cd_8885';
break;
case 2:
img = '1404_0d03ec48b64b4b65a6820aa5a58a39af_5487';
break;
case 3:
img = '1292_5d3c0fde3f83d725eb58025a522a6097_5648';
break;
default:
img = '7395_5d3c0fde3f83d725eb58025a522a6097_4191';
}
img = prefix + img + suffix;
document.getElementById(id).setAttribute('src', img);
// also tried with just ".src =" - didn't worked
}
function check_create_cookie( cookie_name, ident ) {
if( document.cookie.indexOf( cookie_name ) >= 0 ) {
rand_photo( ident )
}
else {
document.cookie = cookie_name + '=1; max-age=60';
}
}
window.onload = function() {
check_create_cookie( 'sample_cookie', 'photo' );
}

<img id="photo" src="../photostock/3129_382a101ee6d307dfd34abad8941c35cd_8885.jpg" alt="background" />