172 lines
5.9 KiB
Markdown
172 lines
5.9 KiB
Markdown
# Preconditions for Node.js
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[](https://travis-ci.org/MathieuTurcotte/node-precond)
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[](http://badge.fury.io/js/precond)
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Precondition checks for Node.js inspired by [Guava's precondition checking
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utilities](https://code.google.com/p/guava-libraries/wiki/PreconditionsExplained).
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## Installation
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```
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npm install precond
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```
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## Unit tests
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```
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npm test
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```
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## Overview
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Precond provides a set of functions to verify arguments and state correctness
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It lets you rewrite constructs like the following
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```js
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if (!this.isConnected) {
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throw new Error('Client should be connected before calling X.');
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}
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```
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into a more compact and declarative check bellow.
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```js
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precond.checkState(this.isConnected, 'Client should be ...');
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```
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**Note that even though the throw statement is wrapped in a function, the call
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stack will still start from the calling function. So the previous examples would
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both produce the same stack trace.**
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All arguments after the message will be used to format the actual error
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message that will be thrown.
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The following precondition checks are provded:
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- checkArgument(value, [messageFormat, [formatArgs, ...]])
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- checkState(value, [messageFormat, [formatArgs, ...]])
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- checkIsDef(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsDefAndNotNull(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsString(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsArray(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsNumber(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsBoolean(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsFunction(value, [messageFormat, [formatArgs, ...]]) -> value
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- checkIsObject(value, [messageFormat, [formatArgs, ...]]) -> value
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## API
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### Static functions
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#### precond.checkArgument(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be truthy
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is true. Throws an `IllegalArgumentError` if value
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is false.
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#### precond.checkState(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be truthy
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is true. Throws an `IllegalStateError` if value
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is false.
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#### precond.checkIsDef(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be defined
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is defined (could be null). Throws an
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`IllegalArgumentError` if value is undefined. Returns the value of
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the value that was validated.
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#### precond.checkIsDefAndNotNull(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be defined and not null
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is defined and not null. Throws an
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`IllegalArgumentError` if value is undefined or null. Returns the value of
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the value that was validated.
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#### precond.checkIsString(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be a string
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is a string or a String object. Throws an
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`IllegalArgumentError` if value isn't a string. Returns the value of
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the value that was validated.
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#### precond.checkIsArray(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be an array
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is an array. Throws an `IllegalArgumentError` if
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value isn't an array. Returns the value of the value that was
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validated.
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#### precond.checkIsNumber(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be a number
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is a number. Throws an `IllegalArgumentError` if
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value isn't a number. Returns the value of the value that was
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validated.
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#### precond.checkIsBoolean(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be a boolean
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is a boolean. Throws an `IllegalArgumentError` if
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value isn't a boolean. Returns the value of the value that was
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validated.
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#### precond.checkIsFunction(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be a function
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is a function. Throws an `IllegalArgumentError` if
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value isn't a function. Returns the value of the value that was
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validated.
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#### precond.checkIsObject(value, [messageFormat, [formatArgs, ...]])
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- value: the value that is required to be an object
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- messageFormat: error message format template
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- formatArgs: arguments to be substituted into the message template
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Ensures that value is an object. Throws an `IllegalArgumentError` if
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value isn't an object. Returns the value of the value that was
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validated.
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### Class precond.IllegalArgumentError
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Extends `Error` and is thrown to signal illegal arguments.
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### Class precond.IllegalStateError
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Extends `Error` and is thrown to signal that the program or object has reached
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an illegal state.
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## License
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This code is free to use under the terms of the [MIT license](http://mturcotte.mit-license.org/).
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