获取jQuery中匹配元素的文本

Question

In the following HTML...

<p>abc<span class='blue'>def</span>ghi</p>

...I want to get the character of text immediately preceding the span element (in this case the letter c ). Assume that the string between the p tags is of arbitrary contents and length, and that the span element could be anywhere in between the p tags. When the opening p tag is adjacent to the opening span tag, an empty string should be returned.

Is there a convenient way to retrieve such with jQuery?

Answer 1

You can use:

var prevLetters = $('span.blue')[0].previousSibling.nodeValue,
    lastLetter = prevLetters.substring(prevLetters.length - 1);

 var prevLetters = $('span.blue')[0].previousSibling.nodeValue; var lastLetter = prevLetters.substring(prevLetters.length - 1); console.log(lastLetter); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <p>abc<span class='blue'>def</span>ghi</p> 

JS Fiddle demo .

This finds all the elements matching the selector and then, using the [0] notation, switches to the DOM node (rather than the jQuery object), and selects the previous sibling (a textNode ) and finds its nodeValue .

This is then modified using the substring() to give only the last letter.

---

Edited : to meet the requirement of an empty string, if the span tag is the first child of the parent:

var prevLetters, lastLetter;
if ($('span.blue')[0].previousSibling) {
    prevLetters = $('span.blue')[0].previousSibling.nodeValue;
    lastLetter = prevLetters.substring(prevLetters.length - 1);
}
else {
    lastLetter = '';
}

 var prevLetters, lastLetter; if ($('span.blue')[0].previousSibling) { prevLetters = $('span.blue')[0].previousSibling.nodeValue; lastLetter = prevLetters.substring(prevLetters.length - 1); } else { lastLetter = ''; } console.log(lastLetter); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <p><span class='blue'>def</span>ghi</p> 

JS Fiddle demo .

---

Edited and turned into a function:

function prevLetter(elem){
    if (!elem){
        return false;
    }
    else {
        var prevLetters, lastLetter;
        if (elem.previousSibling){
            prevLetters = elem
                .previousSibling
                .nodeValue;
            lastLetter = prevLetters
                .substring(prevLetters.length-1);
        }
        else {
            lastLetter = '';
        }
    }
    return lastLetter;
}

var lastLetter = prevLetter($('span.blue')[0]);

 function prevLetter(elem) { if (!elem) { return false; } else { var prevLetters, lastLetter; if (elem.previousSibling) { prevLetters = elem .previousSibling .nodeValue; lastLetter = prevLetters .substring(prevLetters.length - 1); } else { lastLetter = ''; } } return lastLetter; } var lastLetter = prevLetter($('span.blue')[0]); console.log(lastLetter); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <p>abc<span class='blue'>def</span>ghi</p> 

JS Fiddle demo .

And, finally, a pure JavaScript answer which changes the selector from a jQuery selector, utilising document.querySelectorAll() where available, to a DOM selector utilising document.querySelectorAll() directly (all other code remains the same as in the function above):

var lastLetter = prevLetter(document.querySelectorAll('span.blue')[0]);
console.log(lastLetter);

// or:
var lastLetter = prevLetter(document.querySelector('span.blue'));
console.log(lastLetter);

The key difference between the last two is that querySelectorAll() returns a collection of elements, whether that collection has none, one or many elements - and therefore requires the use of an index to retrieve a particular element, whereas querySelector() returns only one – the first – matching Node, or null if no matching nodes were found.

References:

• nodeValue .
• previousSibling .
• substring() .

Answer 2

Here is the expected solution demo on jsfiddle :

Code as below:

var all=$("p").text(); // everything inside <p>
var sub=$("span ").text(); // everything inside <span>
var pos= all.indexOf(sub)-1; // place of just letter before span
alert(all[pos]);​