JS循环-如何知道循环的所有附加条件是否都满足
JS循环-如何知道循环的所有附加条件是否都满足
提问于 2018-08-11 06:16:45
注释在代码中(我只是不知道如何检查是否所有项都满足循环中的条件，如果满足，则执行操作)：
// EDIT -更多真实的例子。
因为工作示例真的很复杂，让我们假设我们只是...测试页面链接(或页面上的任何html元素)。
HTML：
<html>
<head>
<title>Links test</title>
</head>
<body>
<!-- links are random - we do not know how many they are, and how many of them got title attribute -->
<a href="https://www.google.com" title="google">google</a>
<a href="https://facebook.com/">facebook<</a>
<a href="https://www.instagram.com/" title="instagram">instagram</a>
<a href="https://www.amazon.com/">amazon</a>
<a href="https://www.apple.com/" title="apple">apple</a>
</body>
</html>JS：
let links = document.getElementsByTagName('a');
let linksLength = links.length;
let titleCount = 0;
for (i = 0; i < linksLength; i++) {
if (links[i].getAttribute('title') !== undefined) {
// I need to count all loop part that fulfil the condition
titleCount += 1;
// and if it's the last item that fulfil this condition then do something (in this main loop)
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2018-08-11 06:26:47
我建议使用filter方法，然后使用结果来获取计数和最后一个元素。
给定一个数字数组data，下面是一个示例：
relevantData = data.filter(e => [4,5,6].includes(e));
count = relevantData.length;
lastItem = relevantData.slice(-1)Stack Overflow用户
发布于 2018-08-12 03:48:24
let links = document.getElementsByTagName('a');
console.log('======================');
console.log('links HTML collection:\n');
console.log(links);
console.log('======================');
let linksLength = links.length;
let linksTitleCount = 0;
let html = '';
let linksArray = Array.from(links); // converting HTML collection to an array
let allLinksThatDoesHaveTitleAttr = linksArray.filter(function(l)
{
return (l.getAttribute('title') !== undefined && l.getAttribute('title') !== null && l.getAttribute('title') !== '');
});
let allLinksThatDoesHaveTitleAttrCount = allLinksThatDoesHaveTitleAttr.length;
console.log();
console.log('======================');
console.log('allLinksThatDoesHaveTitleAttribute:\n');
console.log(allLinksThatDoesHaveTitleAttrCount);
console.log('======================');
//let lastItem = relevantData.slice(-1)
for (i = 0; i < linksLength; i++) { // main loop throught ALL links
// lets supose we... build html element
html += 'link' + [i] +'\n';
if (links[i].getAttribute('title') !== undefined && links[i].getAttribute('title') !== null && links[i].getAttribute('title') !== '') { // condition that check existance of title attribute - thanks @m_hutley
linksTitleCount += 1; // this is cause I need to count all loop part that fulfil the condition
console.log(linksTitleCount);
console.log();
html += 'this link - ' + [i] + ' - does not have title attribute! \n\n';
if (linksTitleCount == allLinksThatDoesHaveTitleAttrCount)
{
console.log('DONE!'); // we know we are done - we loop throught all elements that does have title attr
// NOW if it's the last item that fulfil this condition then do something (in this main loop) + some async operations that will leater (when data arrive) target specific HTML with specific link (order like in loop - [i])
}
}
}
console.log('HTML result is:\n');
console.log(html);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/51794648
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