I am hoping that I can get some help with my learning and find out what it is about my function that is not working correctly:
function contains() {
var substr = 'bar';
var str = 'foobar';
if (str.indexOf(substr)) {
// Return true if substr is a substring of str
return true;
} else {
// and false if substr is not a substring of str
return false;
};
}
Thank you in advance for anyone who can help me get over this bump in learning.
Rob
indexOf returns -1 if it's not found, and ~-1 === 0 is falsy. Every other number returns truthy with ~ (since all numbers other than 0 are truthy). ~ is the bitwise NOT which has an interesting property that ~-1 === 0.
!! converts to a boolean (truthy becomes true, falsy becomes false).
So you could do:
function contains() {
var substr = 'bar';
var str = 'foobar';
return !!~str.indexOf(substr);
}
You're currently returning true if it's not found (-1 is thruthy), and false if it's at position 0 (0 is falsy).
it's kind of off the topic, but you can write some regex like:
function contains() {
var str = 'foobar';
var substrRegex = /bar/;
return substrRegex.test(str);
}
about javascript test(): http://www.w3schools.com/jsref/jsref_regexp_test.asp
about Regex: http://www.regular-expressions.info/
return str.indexOf(substr) > -1;.