Javascript 条件查找/替换

一种方法如下（使用纯JavaScript，尽管您需要使用最新的浏览器）：

// first, we need to get all the 'li' items:
var lis = document.querySelectorAll('ul > li'),
    // find the relevant text-property for this browser:
    textProp = 'textContent' in document ? 'textContent' : 'innerText',
    // empty string variable to allow assessment of changes:
    _newText = '';
// Remap the bullet list entries to a new (consistent) tag type (your choice – make it look pretty!).
// do this one yourself.
// a function to zero-pad the numbers (I believe a requirement of Dewey Decimal):
function leftPadNumber(num, numLength, padChar) {
    var nString = num.toString(),
        major = parseInt(num, 10),
        minor = parseFloat(nString.substring(nString.indexOf('.'))),
        diff = numLength - major.toString().length;
    if (diff > 0) {
        return new Array(diff + 1).join(padChar || 0) + (major + minor);
    } else {
        return num;
    }
}
// For entries between 100 and 200, add 100 to the Dewey decimal number.
// For entries between 400 and 500, add 200 to the Dewey decimal number.
// Entries between 850 and 900 need to have 100 removed from the Dewey decimal number.
// Entries between 600 and 650 need to have 17 added to the Dewey decimal number
// note that I've taken a very literal interpretation of 'between' (amend if necessary):
function amendedDeweyDecimal(num) {
    if (num > 100 && num < 200) {
        num += 100;
    } else if (num > 400 && num < 500) {
        num += 200;
    } else if (num > 850 && num < 900) {
        num -= 100;
    } else if (num > 600 && num < 650) {
        num += 17;
    }
    // happens if num falls somewhere outside of the above constraints:
    return num;
}
// iterates over each element in the 'lis' nodeList/collection:
[].forEach.call(lis, function (a) {
    /* replaces the found numbers ('m') in the string, using the two
       functions, above, and assigns those to the _newText variable:
    _newText = a[textProp].replace(/('d{3}'.'d{2})/, function (m) {
        return leftPadNumber(amendedDeweyDecimal(parseFloat(m)).toFixed(2), 3);
    });
    // For items that get changed, append “changed” to the record.
    // For items that do not get changed, append “no change” to the record.
    // returns the original text to the element, along with '(no change)'
    // (if 'a[textProp]' is exactly equal to '_newText') or with '(changed)'
    // (if the two variables are not identical):
    a[textProp] = _newText + ' (' + (_newText === a[textProp] ? 'no change' : 'changed') + ')';
});
// For records that are incorrect, append “invalid record” to the record
// I have absolutely no idea how to assess an 'incorrect' record.

JS小提琴演示。

引用：

• Array.prototype.forEach() .
• document.querySelectorAll() .
• Number.toFixed() .
• Number.toString() .
• String.parseFloat() .
• String.parseInt() .
• String.replace() .

试试 jQuery .each

$('li').each(function(index, value) {
    var val = $(this).text().split(','); //split into array
    if (index >= 100 && index < 200) {
        //do stuff
    }
    if (index >= 400 && index < 500) {
        //do stuff
    }
    //etc
});

无论你是想使用纯JavaScript还是辅助库（例如jQuery）来解决这个问题，我都建议把你的问题拆解成更小的任务，然后一个接一个地解决。最后，他们将一个安装到另一个，并将构建完整的解决方案。我会从三个简单的函数开始（阅读您的描述，它们将经常需要）：

• 能够单独列出所有 LI 元素
• 从 LI 内容中提取数字
• 检查数字是否在给定范围内

代码可能如下所示：

// count of all LI items
var elements = 0; 
// fetch LI item one at a time
var element = document.getElementById(elements+1);
while (element != undefined) {
    // get the number
    var number = Number(getNumber(element.innerHTML));
    // do something with number and or LI element
    if (inRange(number, 100, 200)) { /* add 100 ...*/ } // and so on
    // go to next element
    elements++;
    element = document.getElementById(elements+1);
}
function getNumber(elementContent) {
    return elementContent.split(",")[0]; // TODO error handling
}
function inRange(number, min, max) {
    return (number >= min) && (number <= max);
}

您可以引入简单的对象和数组来存储信息和状态，以跟踪内容的更改。