RangeError: repeat count must be non-negative

The JavaScript exception "repeat count must be non-negative" occurs when the String.prototype.repeat() method is used with a count argument that is a negative number.


RangeError: Invalid count value: -1 (V8-based)
RangeError: repeat count must be non-negative (Firefox)
RangeError: String.prototype.repeat argument must be greater than or equal to 0 and not be Infinity (Safari)

Error type

What went wrong?

The String.prototype.repeat() method has been used. It has a count parameter indicating the number of times to repeat the string. It must be between 0 and less than positive Infinity and cannot be a negative number. The range of allowed values can be described like this: [0, +∞).


Invalid cases

'abc'.repeat(-1); // RangeError

Valid cases

'abc'.repeat(0);    // ''
'abc'.repeat(1);    // 'abc'
'abc'.repeat(2);    // 'abcabc'
'abc'.repeat(3.5);  // 'abcabcabc' (count will be converted to integer)

See also