replace-bad-dollar-single-quote.js

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let evil = new RegExp();

// https://tc39.es/ecma262/#sec-getsubstitution

// Input: position = 0

// Step 2: matchLength = 7

// Step 4: stringLength = 3

// Step 8: tailPos = position + matchLength = 7

//

// tailPos ≥ stringLength, so $' is replaced with the empty string.

evil.exec = () => ({ 0: "1234567", length: 1, index: 0 });

assertEq("abc".replace(evil, "$'"), "");

// Input: position = 3

// Step 2: matchLength = 1

// Step 4: stringLength = 3

// Step 8: tailPos = position + matchLength = 4

//

// tailPos ≥ stringLength, so $' is replaced with the empty string.

evil.exec = () => ({ 0: "x", length: 1, index: 3 });

assertEq("abc".replace(evil, "$'"), "abc");

// Input: position = 2

// Step 2: matchLength = 1

// Step 4: stringLength = 3

// Step 8: tailPos = position + matchLength = 3

//

// tailPos ≥ stringLength, so $' is replaced with the empty string.

evil.exec = () => ({ 0: "x", length: 1, index: 2 });

assertEq("abc".replace(evil, "$'"), "ab");

// Input: position = 2

// Step 2: matchLength = 1

// Step 4: stringLength = 4

// Step 8: tailPos = position + matchLength = 3

//

// tailPos < stringLength, so $' is replaced with |"abcd".sustring(tailPos)| = "d".

evil.exec = () => ({ 0: "x", length: 1, index: 2 });

assertEq("abcd".replace(evil, "$'"), "abdd");

// Input: position = 2

// Step 2: matchLength = 1

// Step 4: stringLength = 5

// Step 8: tailPos = position + matchLength = 3

//

// tailPos < stringLength, so $' is replaced with |"abcd".sustring(tailPos)| = "de".

evil.exec = () => ({ 0: "x", length: 1, index: 2 });

assertEq("abcde".replace(evil, "$'"), "abdede");

if (typeof reportCompare === "function")

  reportCompare(0, 0);