You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
77 lines
2.3 KiB
77 lines
2.3 KiB
3 weeks ago
|
"use strict";
|
||
|
|
// Following http://www.w3.org/TR/css3-selectors/#nth-child-pseudo
|
||
|
|
Object.defineProperty(exports, "__esModule", { value: true });
|
||
|
|
exports.parse = void 0;
|
||
|
|
// Whitespace as per https://www.w3.org/TR/selectors-3/#lex is " \t\r\n\f"
|
||
|
|
var whitespace = new Set([9, 10, 12, 13, 32]);
|
||
|
|
var ZERO = "0".charCodeAt(0);
|
||
|
|
var NINE = "9".charCodeAt(0);
|
||
|
|
/**
|
||
|
|
* Parses an expression.
|
||
|
|
*
|
||
|
|
* @throws An `Error` if parsing fails.
|
||
|
|
* @returns An array containing the integer step size and the integer offset of the nth rule.
|
||
|
|
* @example nthCheck.parse("2n+3"); // returns [2, 3]
|
||
|
|
*/
|
||
|
|
function parse(formula) {
|
||
|
|
formula = formula.trim().toLowerCase();
|
||
|
|
if (formula === "even") {
|
||
|
|
return [2, 0];
|
||
|
|
}
|
||
|
|
else if (formula === "odd") {
|
||
|
|
return [2, 1];
|
||
|
|
}
|
||
|
|
// Parse [ ['-'|'+']? INTEGER? {N} [ S* ['-'|'+'] S* INTEGER ]?
|
||
|
|
var idx = 0;
|
||
|
|
var a = 0;
|
||
|
|
var sign = readSign();
|
||
|
|
var number = readNumber();
|
||
|
|
if (idx < formula.length && formula.charAt(idx) === "n") {
|
||
|
|
idx++;
|
||
|
|
a = sign * (number !== null && number !== void 0 ? number : 1);
|
||
|
|
skipWhitespace();
|
||
|
|
if (idx < formula.length) {
|
||
|
|
sign = readSign();
|
||
|
|
skipWhitespace();
|
||
|
|
number = readNumber();
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
sign = number = 0;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
// Throw if there is anything else
|
||
|
|
if (number === null || idx < formula.length) {
|
||
|
|
throw new Error("n-th rule couldn't be parsed ('".concat(formula, "')"));
|
||
|
|
}
|
||
|
|
return [a, sign * number];
|
||
|
|
function readSign() {
|
||
|
|
if (formula.charAt(idx) === "-") {
|
||
|
|
idx++;
|
||
|
|
return -1;
|
||
|
|
}
|
||
|
|
if (formula.charAt(idx) === "+") {
|
||
|
|
idx++;
|
||
|
|
}
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
function readNumber() {
|
||
|
|
var start = idx;
|
||
|
|
var value = 0;
|
||
|
|
while (idx < formula.length &&
|
||
|
|
formula.charCodeAt(idx) >= ZERO &&
|
||
|
|
formula.charCodeAt(idx) <= NINE) {
|
||
|
|
value = value * 10 + (formula.charCodeAt(idx) - ZERO);
|
||
|
|
idx++;
|
||
|
|
}
|
||
|
|
// Return `null` if we didn't read anything.
|
||
|
|
return idx === start ? null : value;
|
||
|
|
}
|
||
|
|
function skipWhitespace() {
|
||
|
|
while (idx < formula.length &&
|
||
|
|
whitespace.has(formula.charCodeAt(idx))) {
|
||
|
|
idx++;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
exports.parse = parse;
|
||
|
|
//# sourceMappingURL=parse.js.map
|