charAtComparisons

Reports comparing charAt() results with strings longer than one character.

✅ This rule is included in the ts logical and logicalStrict presets.

The charAt method returns a string of exactly one character. If the return value is compared with a string of length greater than one, the comparison will always evaluate to the same result. Equality comparisons (===, ==) will always be false, and inequality comparisons (!==, !=) will always be true.


const text: string
text.
String.charAt(pos: number): string
Returns the character at the specified index.
@param ― pos The zero-based index of the desired character.
charAt(0) === "ab";

"abc" === 
const text: string
text.
String.charAt(pos: number): string
Returns the character at the specified index.
@param ― pos The zero-based index of the desired character.
charAt(0);


const text: string
text.
String.charAt(pos: number): string
Returns the character at the specified index.
@param ― pos The zero-based index of the desired character.
charAt(0) !== "hello";


const text: string
text.
String.charAt(pos: number): string
Returns the character at the specified index.
@param ― pos The zero-based index of the desired character.
charAt(0) === "a";


const text: string
text.
String.slice(start?: number, end?: number): string
Returns a section of a string.
@param ― start The index to the beginning of the specified portion of stringObj.
@param ― end The index to the end of the specified portion of stringObj. The substring includes the characters up to, but not including, the character indicated by end.
If this value is not specified, the substring continues to the end of stringObj.
slice(0, 2) === "ab";


const text: string
text.
String.startsWith(searchString: string, position?: number): boolean
Returns true if the sequence of elements of searchString converted to a String is the
same as the corresponding elements of this object (converted to a String) starting at
position. Otherwise returns false.
startsWith("ab");

Options

This rule is not configurable.

When Not To Use It

This rule catches a specific programming error with no legitimate use cases. There is no reason to disable this rule.

Equivalents in Other Linters

Oxlint: oxc/bad-char-at-comparison

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charAtComparisons

Examples

Options

When Not To Use It

Further Reading

Equivalents in Other Linters