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Generate double-equality versus triple-equality test code for TypeScript
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// run this code in your browser console to generate TypeScript test code | |
function generateEqualityTests() | |
{ | |
function stringify(value) | |
{ | |
if (Object.is(value, undefined) || Object.is(value, NaN)) | |
return '' + value; | |
return JSON.stringify(value); | |
} | |
// test cases from http://dorey.github.io/JavaScript-Equality-Table/ | |
let values = [null, undefined, true, false, 1, 0, -1, 'true', 'false', '1', '0', '-1', '', Infinity, -Infinity, [], {}, [[]], [0], [1], NaN]; | |
let tests = []; | |
for (let v1 of values) | |
{ | |
for (let v2 of values) | |
{ | |
let r1 = (v1 == v2); | |
let r2 = (v1 === v2); | |
if (!Object.is(r1, r2)) | |
tests.push(`${stringify(v1)} == ${stringify(v2)}; // ${r1}`); | |
} | |
} | |
return tests.join('\n'); | |
} | |
console.log(generateEqualityTests()); |
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// This is the output of generateEqualityTests() and the resulting TypeScript errors. | |
null == undefined; // true (no error) | |
undefined == null; // true (no error) | |
true == 1; // error TS2365: Operator '==' cannot be applied to types 'true' and '1'. | |
true == "1"; // error TS2365: Operator '==' cannot be applied to types 'true' and '"1"'. | |
true == [1]; // error TS2365: Operator '==' cannot be applied to types 'boolean' and 'number[]'. | |
false == 0; // error TS2365: Operator '==' cannot be applied to types 'false' and '0'. | |
false == "0"; // error TS2365: Operator '==' cannot be applied to types 'false' and '"0"'. | |
false == ""; // error TS2365: Operator '==' cannot be applied to types 'false' and '""'. | |
false == []; // error TS2365: Operator '==' cannot be applied to types 'boolean' and 'undefined[]'. | |
false == [[]]; // error TS2365: Operator '==' cannot be applied to types 'boolean' and 'undefined[][]'. | |
false == [0]; // error TS2365: Operator '==' cannot be applied to types 'boolean' and 'number[]'. | |
1 == true; // error TS2365: Operator '==' cannot be applied to types '1' and 'true'. | |
1 == "1"; // error TS2365: Operator '==' cannot be applied to types '1' and '"1"'. | |
1 == [1]; // error TS2365: Operator '==' cannot be applied to types 'number' and 'number[]'. | |
0 == false; // error TS2365: Operator '==' cannot be applied to types '0' and 'false'. | |
0 == "0"; // error TS2365: Operator '==' cannot be applied to types '0' and '"0"'. | |
0 == ""; // error TS2365: Operator '==' cannot be applied to types '0' and '""'. | |
0 == []; // error TS2365: Operator '==' cannot be applied to types 'number' and 'undefined[]'. | |
0 == [[]]; // error TS2365: Operator '==' cannot be applied to types 'number' and 'undefined[][]'. | |
0 == [0]; // error TS2365: Operator '==' cannot be applied to types 'number' and 'number[]'. | |
-1 == "-1"; // error TS2365: Operator '==' cannot be applied to types '-1' and '"-1"'. | |
"1" == true; // error TS2365: Operator '==' cannot be applied to types '"1"' and 'true'. | |
"1" == 1; // error TS2365: Operator '==' cannot be applied to types '"1"' and '1'. | |
"1" == [1]; // error TS2365: Operator '==' cannot be applied to types 'string' and 'number[]'. | |
"0" == false; // error TS2365: Operator '==' cannot be applied to types '"0"' and 'false'. | |
"0" == 0; // error TS2365: Operator '==' cannot be applied to types '"0"' and '0'. | |
"0" == [0]; // error TS2365: Operator '==' cannot be applied to types 'string' and 'number[]'. | |
"-1" == -1; // error TS2365: Operator '==' cannot be applied to types '"-1"' and '-1'. | |
"" == false; // error TS2365: Operator '==' cannot be applied to types '""' and 'false'. | |
"" == 0; // error TS2365: Operator '==' cannot be applied to types '""' and '0'. | |
"" == []; // error TS2365: Operator '==' cannot be applied to types 'string' and 'undefined[]'. | |
"" == [[]]; // error TS2365: Operator '==' cannot be applied to types 'string' and 'undefined[][]'. | |
[] == false; // error TS2365: Operator '==' cannot be applied to types 'undefined[]' and 'boolean'. | |
[] == 0; // error TS2365: Operator '==' cannot be applied to types 'undefined[]' and 'number'. | |
[] == ""; // error TS2365: Operator '==' cannot be applied to types 'undefined[]' and 'string'. | |
[[]] == false; // error TS2365: Operator '==' cannot be applied to types 'undefined[][]' and 'boolean'. | |
[[]] == 0; // error TS2365: Operator '==' cannot be applied to types 'undefined[][]' and 'number'. | |
[[]] == ""; // error TS2365: Operator '==' cannot be applied to types 'undefined[][]' and 'string'. | |
[0] == false; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'boolean'. | |
[0] == 0; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'number'. | |
[0] == "0"; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'string'. | |
[1] == true; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'boolean'. | |
[1] == 1; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'number'. | |
[1] == "1"; // error TS2365: Operator '==' cannot be applied to types 'number[]' and 'string'. |
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