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2 years ago
'use strict';
var GetIntrinsic = require('get-intrinsic');
var $Number = GetIntrinsic('%Number%');
var $TypeError = GetIntrinsic('%TypeError%');
var $isNaN = require('../helpers/isNaN');
var IsStringPrefix = require('./IsStringPrefix');
var StringToBigInt = require('./StringToBigInt');
var ToNumeric = require('./ToNumeric');
var ToPrimitive = require('./ToPrimitive');
var Type = require('./Type');
var BigIntLessThan = require('./BigInt/lessThan');
var NumberLessThan = require('./Number/lessThan');
// https://262.ecma-international.org/13.0/#sec-islessthan
// eslint-disable-next-line max-statements, max-lines-per-function
module.exports = function IsLessThan(x, y, LeftFirst) {
if (Type(LeftFirst) !== 'Boolean') {
throw new $TypeError('Assertion failed: LeftFirst argument must be a Boolean');
}
var px;
var py;
if (LeftFirst) {
px = ToPrimitive(x, $Number);
py = ToPrimitive(y, $Number);
} else {
py = ToPrimitive(y, $Number);
px = ToPrimitive(x, $Number);
}
var pxType = Type(px);
var pyType = Type(py);
if (pxType === 'String' && pyType === 'String') {
if (IsStringPrefix(py, px)) {
return false;
}
if (IsStringPrefix(px, py)) {
return true;
}
/*
c. Let k be the smallest non-negative integer such that the code unit at index k within px is different from the code unit at index k within py. (There must be such a k, for neither String is a prefix of the other.)
d. Let m be the integer that is the numeric value of the code unit at index k within px.
e. Let n be the integer that is the numeric value of the code unit at index k within py.
f. If m < n, return true. Otherwise, return false.
*/
return px < py; // both strings, neither a prefix of the other. shortcut for steps 3 c-f
}
var nx;
var ny;
if (pxType === 'BigInt' && pyType === 'String') {
ny = StringToBigInt(py);
if ($isNaN(ny)) {
return void undefined;
}
return BigIntLessThan(px, ny);
}
if (pxType === 'String' && pyType === 'BigInt') {
nx = StringToBigInt(px);
if ($isNaN(nx)) {
return void undefined;
}
return BigIntLessThan(nx, py);
}
nx = ToNumeric(px);
ny = ToNumeric(py);
var nxType = Type(nx);
if (nxType === Type(ny)) {
return nxType === 'Number' ? NumberLessThan(nx, ny) : BigIntLessThan(nx, ny);
}
if ($isNaN(nx) || $isNaN(ny)) {
return void undefined;
}
if (nx === -Infinity || ny === Infinity) {
return true;
}
if (nx === Infinity || ny === -Infinity) {
return false;
}
return nx < ny; // by now, these are both nonzero, finite, and not equal
};