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/**
* @fileoverview A rule to control the style of variable initializations.
* @author Colin Ihrig
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a given node is a for loop.
* @param {ASTNode} block - A node to check.
* @returns {boolean} `true` when the node is a for loop.
*/
function isForLoop(block) {
return block.type === "ForInStatement" ||
block.type === "ForOfStatement" ||
block.type === "ForStatement";
}
/**
* Checks whether or not a given declarator node has its initializer.
* @param {ASTNode} node - A declarator node to check.
* @returns {boolean} `true` when the node has its initializer.
*/
function isInitialized(node) {
const declaration = node.parent;
const block = declaration.parent;
if (isForLoop(block)) {
if (block.type === "ForStatement") {
return block.init === declaration;
}
return block.left === declaration;
}
return Boolean(node.init);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "require or disallow initialization in variable declarations",
category: "Variables",
recommended: false,
url: "https://eslint.org/docs/rules/init-declarations"
},
schema: {
anyOf: [
{
type: "array",
items: [
{
enum: ["always"]
}
],
minItems: 0,
maxItems: 1
},
{
type: "array",
items: [
{
enum: ["never"]
},
{
type: "object",
properties: {
ignoreForLoopInit: {
type: "boolean"
}
},
additionalProperties: false
}
],
minItems: 0,
maxItems: 2
}
]
},
messages: {
initialized: "Variable '{{idName}}' should be initialized on declaration.",
notInitialized: "Variable '{{idName}}' should not be initialized on declaration."
}
},
create(context) {
const MODE_ALWAYS = "always",
MODE_NEVER = "never";
const mode = context.options[0] || MODE_ALWAYS;
const params = context.options[1] || {};
//--------------------------------------------------------------------------
// Public API
//--------------------------------------------------------------------------
return {
"VariableDeclaration:exit"(node) {
const kind = node.kind,
declarations = node.declarations;
for (let i = 0; i < declarations.length; ++i) {
const declaration = declarations[i],
id = declaration.id,
initialized = isInitialized(declaration),
isIgnoredForLoop = params.ignoreForLoopInit && isForLoop(node.parent);
let messageId = "";
if (mode === MODE_ALWAYS && !initialized) {
messageId = "initialized";
} else if (mode === MODE_NEVER && kind !== "const" && initialized && !isIgnoredForLoop) {
messageId = "notInitialized";
}
if (id.type === "Identifier" && messageId) {
context.report({
node: declaration,
messageId,
data: {
idName: id.name
}
});
}
}
}
};
}
};
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