1360289 - String.prototype based function throws on using this.valueOf() sometimes

Status: RESOLVED INVALID

(Core :: JavaScript Engine, defect)

Description

[Jim Michaels]

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:53.0) Gecko/20100101 Firefox/53.0
Build ID: 20170413192749

Steps to reproduce:

String.prototype.reverse=function() {
	var s2="",i;
	for (i=0; i < this.ValueOf().length; i++) {
		s2+=s[this.ValueOf().length-1-i];
	}
	return s2;
}



Actual results:

TypeError: this.ValueOf is not a function[Learn More]  atoi64.js:232:16


Expected results:

should have just worked. is this causing problems in your code somewhere maybe?

Comment 1

[Jim Michaels]

workaround:
String.prototype.reverse=function() {
	var s2="",i,s=this.valueOf();
	for (i=0; i < s.length; i++) {
		s2+=s[s.length-1-i];
	}
	return s2;
}

Comment 2

[Till Schneidereit [:till]]

Property names are case-sensitive in JS, and the reverse function incorrectly spells ValueOf with an uppercase V. (Besides, valueOf isn't needed at all here and will likely lead to decreased performance.)