I want to check if string b is completely contained in string a.
I tried:
var a = "helloworld"; var b = "wold"; if(a.indexOf(b)) { document.write('yes'); } else { document.write('no'); } The output is yes, it is not my expected output, because string b(wold) is not completely contained in string a(helloworld) --- wold v.s. world
Any suggestion to check the string?
Read the documentation: MDC String.indexOf :)
indexOf returns the index the match was found. This may be 0 (which means "found at the beginning of string") and 0 is a falsy value.
indexOf will return -1 if the needle was not found (and -1 is a truthy value). Thus the logic on the test needs to be adjusted to work using these return codes. String found (at beginning or elsewhere): index >= 0 or index > -1 or index != -1; String not found: index < 0 or index == -1.
Happy coding.
You need to use if(a.indexOf(b) > -1) instead. indexOf returns -1 when it can't find a string.
.indexOf returns -1 if no match was found, which is a truthy value. You'll need to check more explicitly:
if (a.indexOf(b) != -1) That's because indexOf returns -1 if a value is not found:
if(a.indexOf(b) != -1) { you may want to use this
if(a.indexOf(b) != -1) You need to test if the result is -1. -1 indicates no match, but evaluates to true in a boolean sense.
var a = "helloworld"; var b = "wold"; if(a.indexOf(b) > -1) { document.write('yes'); } else { document.write('no'); } 