使用Javascript正则表达式解析CSS渐变规则 [英] parse css gradient rule with Javascript regex
问题描述
在我的css文件中,我有渐变规则,如下所示:
in my css file I have gradient rule, like this:
background-image:linear-gradient(to right, #FF0000 0%, #00FF00 20px, rgb(0, 0, 255) 100%);
我想获取此字符串的所有部分.预期输出为:
I want to get all parts of this string. Expected output is:
linear-gradient
to right
#FF0000
0%,
#00FF00
20px,
rgb(0, 0, 255)
100%
我很难处理整个字符串,所以我决定将其拆分为多个部分.
it was too difficult for me to work on whole string so I decided to split it into parts.
线性渐变
.*gradient[^\(]?
颜色
rgb ?\([ 0-9.%,]+?\)|#[0-9a-fA-F]{3,6}\s[0-9]{1,3}[%|px]|#[0-9a-fA-F]{3,6}|(aqua|black|blue|fuchsia|gray|green|lime|maroon|navy|olive|orange|purple|red|silver|teal|white|yellow){1}(\s[0-9]{1,3}\s*[%|px]?)?
向右
(?<=\()(.*(top|left|right|bottom|center).*?)(?=,)
,但是最后一个正则表达式在JS中不起作用,因为它没有后面的正则表达式. 很快,我需要在这里获得("和,"之间的所有内容
but the last regex not works in JS because it doesn't have regex lookbehind. Shortly, I need here to get all between "(" and ","
推荐答案
解析CSS可能要复杂得多,要记住的事情很少:
Parsing CSS can be far more complex there are few things to remember:
- 避免编写解析器-其他人可能已经写了一个解析器(搜索).
- 如果您不控制输入源或不使用输入样本对其进行全面测试,则解析器可能会失败.
- 在渐变的情况下,您可以具有角度"以及角"等右".
- 色标数量未知(最少1个).
- 您永远不会希望在正则表达式中包含CSS颜色的完整列表(例如
red
,blue
等). - 您应该查看 MDN 以获得详细信息关于语法变化,下面的示例代码仅支持标准语法.
- 根据浏览器和版本的不同,对正则表达式的支持和错误也有所不同-使用所有示例测试目标浏览器.
- Avoid writing a parser - someone else will probably have written one already (search).
- Your parser will likely fail if you don't control the input source or test it thoroughly with input samples.
- In the case of gradients you can have "angles" as well as "corner-sides" like "right".
- There are an unknown number of color stops (minimum 1).
- You will never likely want to include the complete list of CSS colors in a regular expression (e.g.
red
,blue
, etc). - You should check out MDN for details of syntax variations, the sample code below only supports the standard syntax.
- Regular expression support and bugs are different depending on the browser and version - test your target browsers with all your samples.
好的,所以这是一个疯狂的示例,说明您如何使用正则表达式来解析"渐变-我并不是说您应该这样做.
OK, so here is a crazy example of how you "could" parse the gradient using regular expressions - I'm not saying you should.
在这里,我在代码中构建了正则表达式,以保持代码的一定程度的可读性和可维护性.
Here I build my regular expressions in code to keep some level of readability and maintainability of the code.
test_this_thing
函数console.log(result);
的最终输出如下:
The final output of the test_this_thing
functions console.log(result);
is as follows:
输入:
background-image:linear-gradient(to right bottom, #FF0000 0%, #00FF00 20px, rgb(0, 0, 255) 100%);
输出:
{
original:"to right bottom, #FF0000 0%, #00FF00 20px, rgb(0, 0, 255) 100%",
line:"to right bottom",
sideCorner:"right bottom",
colorStopList:[
{
color:"#FF0000",
position:"0%"
},
{
color:"#00FF00",
position:"20px"
},
{
color:"rgb(0, 0, 255)",
position:"100%"
}
]
}
请注意,输出包含original
属性-看起来像输入-但如果输入的一部分不匹配,则input
和original
值将不同;注意到解析器中可能存在错误.
Note the output includes the original
property - this looks like the input - but if part of the input wasn't matched the input
and original
values would be different; noting an possible error in the parser.
以下是来源:
/**
* Utility combine multiple regular expressions.
*
* @param {RegExp[]|string[]} regexpList List of regular expressions or strings.
* @param {string} flags Normal RegExp flags.
*/
var combineRegExp = function (regexpList, flags) {
var i,
source = '';
for (i = 0; i < regexpList.length; i++) {
if (typeof regexpList[i] === 'string') {
source += regexpList[i];
} else {
source += regexpList[i].source;
}
}
return new RegExp(source, flags);
};
/**
* Generate the required regular expressions once.
*
* Regular Expressions are easier to manage this way and can be well described.
*
* @result {object} Object containing regular expressions.
*/
var generateRegExp = function () {
// Note any variables with "Capture" in name include capturing bracket set(s).
var searchFlags = 'gi', // ignore case for angles, "rgb" etc
rAngle = /(?:[+-]?\d*\.?\d+)(?:deg|grad|rad|turn)/, // Angle +ive, -ive and angle types
rSideCornerCapture = /to\s+((?:(?:left|right)(?:\s+(?:top|bottom))?))/, // optional 2nd part
rComma = /\s*,\s*/, // Allow space around comma.
rColorHex = /\#(?:[a-f0-9]{6}|[a-f0-9]{3})/, // 3 or 6 character form
rDigits3 = /\(\s*(?:\d{1,3}\s*,\s*){2}\d{1,3}\s*\)/,// "(1, 2, 3)"
rDigits4 = /\(\s*(?:\d{1,3}\s*,\s*){2}\d{1,3}\s*,\s*\d*\.?\d+\)/,// "(1, 2, 3, 4)"
rValue = /(?:[+-]?\d*\.?\d+)(?:%|[a-z]+)?/,// ".9", "-5px", "100%".
rKeyword = /[_a-z-][_a-z0-9-]*/,// "red", "transparent", "border-collapse".
rColor = combineRegExp([
'(?:', rColorHex, '|', '(?:rgb|hsl)', rDigits3, '|', '(?:rgba|hsla)', rDigits4, '|', rKeyword, ')'
], ''),
rColorStop = combineRegExp([rColor, '(?:\\s+', rValue, '(?:\\s+', rValue, ')?)?'], ''),// Single Color Stop, optional %, optional length.
rColorStopList = combineRegExp(['(?:', rColorStop, rComma, ')*', rColorStop], ''),// List of color stops min 1.
rLineCapture = combineRegExp(['(?:(', rAngle, ')|', rSideCornerCapture, ')'], ''),// Angle or SideCorner
rGradientSearch = combineRegExp([
'(?:(', rLineCapture, ')', rComma, ')?(', rColorStopList, ')'
], searchFlags),// Capture 1:"line", 2:"angle" (optional), 3:"side corner" (optional) and 4:"stop list".
rColorStopSearch = combineRegExp([
'\\s*(', rColor, ')', '(?:\\s+', '(', rValue, '))?', '(?:', rComma, '\\s*)?'
], searchFlags);// Capture 1:"color" and 2:"position" (optional).
return {
gradientSearch: rGradientSearch,
colorStopSearch: rColorStopSearch
};
};
/**
* Actually parse the input gradient parameters string into an object for reusability.
*
*
* @note Really this only supports the standard syntax not historical versions, see MDN for details
* https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient
*
* @param regExpLib
* @param {string} input Input string in the form "to right bottom, #FF0 0%, red 20px, rgb(0, 0, 255) 100%"
* @returns {object|undefined} Object containing break down of input string including array of stop points.
*/
var parseGradient = function (regExpLib, input) {
var result,
matchGradient,
matchColorStop,
stopResult;
// reset search position, because we reuse regex.
regExpLib.gradientSearch.lastIndex = 0;
matchGradient = regExpLib.gradientSearch.exec(input);
if (matchGradient !== null) {
result = {
original: matchGradient[0],
colorStopList: []
};
// Line (Angle or Side-Corner).
if (!!matchGradient[1]) {
result.line = matchGradient[1];
}
// Angle or undefined if side-corner.
if (!!matchGradient[2]) {
result.angle = matchGradient[2];
}
// Side-corner or undefined if angle.
if (!!matchGradient[3]) {
result.sideCorner = matchGradient[3];
}
// reset search position, because we reuse regex.
regExpLib.colorStopSearch.lastIndex = 0;
// Loop though all the color-stops.
matchColorStop = regExpLib.colorStopSearch.exec(matchGradient[4]);
while (matchColorStop !== null) {
stopResult = {
color: matchColorStop[1]
};
// Position (optional).
if (!!matchColorStop[2]) {
stopResult.position = matchColorStop[2];
}
result.colorStopList.push(stopResult);
// Continue searching from previous position.
matchColorStop = regExpLib.colorStopSearch.exec(matchGradient[4]);
}
}
// Can be undefined if match not found.
return result;
};
var test_this_one = function (regExpLib, input) {
var result,
rGradientEnclosedInBrackets = /.*gradient\s*\(((?:\([^\)]*\)|[^\)\(]*)*)\)/,// Captures inside brackets - max one additional inner set.
match = rGradientEnclosedInBrackets.exec(input);
if (match !== null) {
// Get the parameters for the gradient
result = parseGradient(regExpLib, match[1]);
if (result.original.trim() !== match[1].trim()) {
// Did not match the input exactly - possible parsing error.
result.parseWarning = true;
}
} else {
result = "Failed to find gradient";
}
return result;
};
var test_this_thing = function () {
var result = [],
regExpLib = generateRegExp(),
testSubjects = [
// Original question sample
'background-image:linear-gradient(to right bottom, #FF0000 0%, #00FF00 20px, rgb(0, 0, 255) 100%);',
// Sample to test RGBA values (1)
'background-image:linear-gradient(to right bottom, rgba(255, 0, 0, .1) 0%, rgba(0, 255, 0, 0.9) 20px);',
// Sample to test optional gradient line
'background-image:linear-gradient(#FF0000 0%, #00FF00 20px, rgb(0, 0, 255) 100%);',
// Angle, named colors
'background: linear-gradient(45deg, red, blue);',
// Gradient that starts at 60% of the gradient line
'background: linear-gradient(135deg, orange, orange 60%, cyan);',
// Gradient with multi-position color stops
'background: linear-gradient(to right, red 20%, orange 20% 40%, yellow 40% 60%, green 60% 80%, blue 80%);'
];
for (var i = 0; i < testSubjects.length; i++) {
result.push(test_this_one(regExpLib, testSubjects[i]));
}
console.log(result);
};
test_this_thing();
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