Source code
Revision control
Copy as Markdown
Other Tools
// Test String.prototype.at with negative and non-negative indices.
function* characters(...ranges) {
for (let [start, end] of ranges) {
for (let i = start; i <= end; ++i) {
yield i;
}
}
}
const empty = [];
const ascii = [...characters(
[0x41, 0x5A], // A..Z
[0x61, 0x7A], // a..z
)];
const latin1 = [...characters(
[0xC0, 0xFF], // À..ÿ
)];
const twoByte = [...characters(
[0x100, 0x17E], // Ā..ž
)];
function atomize(s) {
return Object.keys({[s]: 0})[0];
}
function codePoints() {
return [empty, ascii, latin1, twoByte];
}
function toRope(s) {
// Ropes have at least two characters.
if (s.length < 2) {
return s;
}
if (s.length === 2) {
return newRope(s[0], s[1]);
}
return newRope(s[0], s.substring(1));
}
function makeStrings() {
let strings = codePoints()
.map(codePoints => String.fromCodePoint(...codePoints))
.flatMap(x => [
x,
toRope(x),
newString(x, {twoByte: true}),
atomize(x),
]);
return strings;
}
function testNonNegativeIndexConstant() {
let strings = makeStrings();
for (let i = 0; i < 200; ++i) {
let str = strings[i % strings.length];
let index = 0;
let ch = str.at(index);
let expected = str.charAt(index);
if (expected === "") expected = undefined;
assertEq(ch, expected);
}
}
for (let i = 0; i < 2; ++i) {
testNonNegativeIndexConstant();
}
function testNonNegativeIndex() {
let strings = makeStrings();
for (let i = 0; i < 200; ++i) {
let str = strings[i % strings.length];
let index = i & 3;
let ch = str.at(index);
let expected = str.charAt(index);
if (expected === "") expected = undefined;
assertEq(ch, expected);
}
}
for (let i = 0; i < 2; ++i) {
testNonNegativeIndex();
}
function testNegativeIndexConstant() {
let strings = makeStrings();
for (let i = 0; i < 200; ++i) {
let str = strings[i % strings.length];
let index = -1;
let ch = str.at(index);
let expected = str.charAt(str.length + index);
if (expected === "") expected = undefined;
assertEq(ch, expected);
}
}
for (let i = 0; i < 2; ++i) {
testNegativeIndexConstant();
}
function testNegativeIndex() {
let strings = makeStrings();
for (let i = 0; i < 200; ++i) {
let str = strings[i % strings.length];
let index = -(i & 3) - 1;
let ch = str.at(index);
let expected = str.charAt(str.length + index);
if (expected === "") expected = undefined;
assertEq(ch, expected);
}
}
for (let i = 0; i < 2; ++i) {
testNegativeIndex();
}