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.
Message
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, +∞).
Examples
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)