@abdullah2993/expression-parser 中文文档教程
expression-parser
用打字稿编写的表达式求值器,目标是支持 SQL
之类的 WHERE
子句。
Installation
npm install --save @abdullah2993/expression-parser
Supported Operations and Functions
Arithmetics
+
-
*
/
Comparison
=
<>
>
>=
<=
Logical
and
or
SQL
IS NULL
IS NOT NULL
BETWEEN [NUMBER] AND [NUMBER]
CASE WHEN expression THEN expression [WHEN expression] [ELSE expression] END
Functions
目前唯一被评估的函数是 LENGTH(variable)
函数,但支持解析器级别的函数调用,因此添加更多 SQL
函数相当容易。
Examples
/** Basic Math **/
evaluate('1+2'));
// 3
evaluate('10 + 2 * 6'));
// 22
evaluate('100 * 2 + 12'));
// 212
evaluate('100 * ( 2 + 12 )'));
// 1400
evaluate('100 * ( 2 + 12 ) / 14'));
// 100
/** Basic Math With Variable Substitution**/
const context = {
a: 1, b: 2, c: 10, d: 6, e: 100, f: 12, g: 14,
};
evaluateObject('a+b', context));
// 3
evaluateObject('c + b * d', context));
// 22
evaluateObject('e * b + f', context));
// 212
evaluateObject('e * ( b + f )', context));
// 1400
evaluateObject('e * ( b + f ) / g', context));
// 100
/** Other Operations **/
const val: any = { a: null };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val = { a: '123' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val = { a: '1234' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// true
const val = { a: '1234567890' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// true
const val = { a: '12345678901' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val: any = { a: 1, b: 1 };
evaluateObject('a is not null and b is not null', val);
// true
evaluateObject('a is not null and b is null', val);
// false
const val = { a: 1, b: null };
evaluateObject('a is not null and b is null', val);
// true
const val = { a: 1, b: 1 };
evaluateObject('a=b', val));
// true
evaluateObject('a>b', val));
// false
evaluateObject('a<b', val));
// false
const val = { a: 1, b: 2 };
evaluateObject('a=b', val);
// false
evaluateObject('a>b', val);
// false
evaluateObject('a<b', val);
// true
Sample AST
//Expression: a is not null and length(a) between 4 and 10
{
"operator": "and",
"left": {
"operator": "<>",
"left": {
"name": "a",
"type": "IdentifierExpression"
},
"right": {
"value": null,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"right": {
"operator": "and",
"left": {
"operator": ">=",
"left": {
"name": "length",
"args": [
{
"name": "a",
"type": "IdentifierExpression"
}
],
"type": "FunctionCallExpression"
},
"right": {
"value": 4,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"right": {
"operator": "<=",
"left": {
"name": "length",
"args": [
{
"name": "a",
"type": "IdentifierExpression"
}
],
"type": "FunctionCallExpression"
},
"right": {
"value": 10,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"type": "BinaryExpression"
},
"type": "BinaryExpression"
}
Test Coverage
13 specs, 0 failures
Finished in 0.069 seconds
Randomized with seed 62175 (jasmine --random=true --seed=62175)
--------------|---------|----------|---------|---------|-----------------------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
--------------|---------|----------|---------|---------|-----------------------------------
All files | 93.24 | 83.33 | 92.73 | 93.19 |
ast.ts | 89.66 | 100 | 90 | 90 | 16-18
evaluator.ts | 85 | 69.23 | 100 | 84.21 | 14,18,27,47-49,64
lexer.ts | 99.04 | 98 | 100 | 99.03 | 86
parser.ts | 89.89 | 70 | 89.47 | 89.41 | 83,91,103,121,133,137,144,181,184
token.ts | 97.06 | 100 | 75 | 96.97 | 44
--------------|---------|----------|---------|---------|-----------------------------------
expression-parser
An expression evaluator written in typescript with the goal to support SQL
like WHERE
clauses.
Installation
npm install --save @abdullah2993/expression-parser
Supported Operations and Functions
Arithmetics
+
-
*
/
Comparison
=
<>
>
>=
<=
Logical
and
or
SQL
IS NULL
IS NOT NULL
BETWEEN [NUMBER] AND [NUMBER]
CASE WHEN expression THEN expression [WHEN expression] [ELSE expression] END
Functions
Currently only function that is evaluated is the LENGTH(variable)
function but supports function calls at the parser level so it is fairly easy to add more SQL
functions.
Examples
/** Basic Math **/
evaluate('1+2'));
// 3
evaluate('10 + 2 * 6'));
// 22
evaluate('100 * 2 + 12'));
// 212
evaluate('100 * ( 2 + 12 )'));
// 1400
evaluate('100 * ( 2 + 12 ) / 14'));
// 100
/** Basic Math With Variable Substitution**/
const context = {
a: 1, b: 2, c: 10, d: 6, e: 100, f: 12, g: 14,
};
evaluateObject('a+b', context));
// 3
evaluateObject('c + b * d', context));
// 22
evaluateObject('e * b + f', context));
// 212
evaluateObject('e * ( b + f )', context));
// 1400
evaluateObject('e * ( b + f ) / g', context));
// 100
/** Other Operations **/
const val: any = { a: null };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val = { a: '123' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val = { a: '1234' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// true
const val = { a: '1234567890' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// true
const val = { a: '12345678901' };
evaluateObject('a is not null and length(a) between 4 and 10', val);
// false
const val: any = { a: 1, b: 1 };
evaluateObject('a is not null and b is not null', val);
// true
evaluateObject('a is not null and b is null', val);
// false
const val = { a: 1, b: null };
evaluateObject('a is not null and b is null', val);
// true
const val = { a: 1, b: 1 };
evaluateObject('a=b', val));
// true
evaluateObject('a>b', val));
// false
evaluateObject('a<b', val));
// false
const val = { a: 1, b: 2 };
evaluateObject('a=b', val);
// false
evaluateObject('a>b', val);
// false
evaluateObject('a<b', val);
// true
Sample AST
//Expression: a is not null and length(a) between 4 and 10
{
"operator": "and",
"left": {
"operator": "<>",
"left": {
"name": "a",
"type": "IdentifierExpression"
},
"right": {
"value": null,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"right": {
"operator": "and",
"left": {
"operator": ">=",
"left": {
"name": "length",
"args": [
{
"name": "a",
"type": "IdentifierExpression"
}
],
"type": "FunctionCallExpression"
},
"right": {
"value": 4,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"right": {
"operator": "<=",
"left": {
"name": "length",
"args": [
{
"name": "a",
"type": "IdentifierExpression"
}
],
"type": "FunctionCallExpression"
},
"right": {
"value": 10,
"type": "ValueExpression"
},
"type": "BinaryExpression"
},
"type": "BinaryExpression"
},
"type": "BinaryExpression"
}
Test Coverage
13 specs, 0 failures
Finished in 0.069 seconds
Randomized with seed 62175 (jasmine --random=true --seed=62175)
--------------|---------|----------|---------|---------|-----------------------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
--------------|---------|----------|---------|---------|-----------------------------------
All files | 93.24 | 83.33 | 92.73 | 93.19 |
ast.ts | 89.66 | 100 | 90 | 90 | 16-18
evaluator.ts | 85 | 69.23 | 100 | 84.21 | 14,18,27,47-49,64
lexer.ts | 99.04 | 98 | 100 | 99.03 | 86
parser.ts | 89.89 | 70 | 89.47 | 89.41 | 83,91,103,121,133,137,144,181,184
token.ts | 97.06 | 100 | 75 | 96.97 | 44
--------------|---------|----------|---------|---------|-----------------------------------