Add prefer-string-slice rule - fixes #65

index.js

@@ -22,7 +22,8 @@ module.exports = {
 				'unicorn/number-literal-case': 'error',
 				'unicorn/no-array-instanceof': 'error',
 				'unicorn/no-new-buffer': 'error',
-				'unicorn/no-hex-escape': 'error'
+				'unicorn/no-hex-escape': 'error',
+				'unicorn/prefer-string-slice': 'error'
 			}
 		}
 	}

rules/prefer-string-slice.js

@@ -0,0 +1,20 @@
+'use strict';
+
+const create = context => {
+	return {
+		Identifier: node => {
+			const name = node.name;
+
+			if (name === 'substr' || name === 'substring') {
+				context.report({
+					node,
+					message: 'Use String.slice instead of String.substr or String.substring.'
+				});
+			}
+		}
+	};
+};
+
+module.exports = {
+	create
+};

test/prefer-string-slice.js

@@ -0,0 +1,47 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/prefer-string-slice';
+
+const ruleTester = avaRuleTester(test, {
+	env: {
+		es6: true
+	}
+});
+
+const error = {
+	ruleId: 'prefer-string-slice',
+	message: 'Use String.slice instead of String.substr or String.substring.'
+};
+
+ruleTester.run('prefer-string-slice', rule, {
+	valid: [
+		'const foo = bar.slice(1)',
+		`const foo = bar.slice(function() { return 1; }, 2);`
+	],
+	invalid: [
+		{
+			code: 'const foo = bar.substr(1)',
+			errors: [error]
+		},
+		{
+			code: 'const foo = bar.substr(1,2)',
+			errors: [error]
+		},
+		{
+			code: `const foo = bar.substr(function() { return 1; }, 2);`,
+			errors: [error]
+		},
+		{
+			code: 'const foo = bar.substring(1)',
+			errors: [error]
+		},
+		{
+			code: 'const foo = bar.substring(1,2)',
+			errors: [error]
+		},
+		{
+			code: `const foo = bar.substr(function() { return 1; }, 2);`,
+			errors: [error]
+		}
+	]
+});