Algorithm Truncate A String - ashish9342/FreeCodeCamp GitHub Wiki
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We need to reduce the length of the string or truncate it if it is longer than the given maximum lengths specified and add ...
to the end. If it is not that long then we keep it as is.
Strings are immutable in JavaScript so we will need a new variable to store the truncated string.
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You will need to use the slice() method and specify where to start and where to stop.
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Do not forget that when we truncate the word, we also must count the length added by ...
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Solution ahead!
function truncateString(str, num) {
// Clear out that junk in your trunk
if (str.length > num && num > 3) {
return str.slice(0, (num - 3)) + '...';
} else if (str.length > num && num <= 3) {
return str.slice(0, num) + '...';
} else {
return str;
}
}
🚀 Run Code
- First we start off with a simple
if
statement to determine one of three outcomes...
- If our string length is greater than the
num
we want to truncate at, and our truncate point is at least three characters or more into the string, we return a slice of our string starting at character 0, and ending atnum - 3
. We then append our'...'
to the end of the string. - However, if our string length is greater than the
num
butnum
is within the first three characters, we don't have to count our dots as characters. Therefore, we return the same string as above, with one difference: The endpoint of our slice is now justnum
. - Finally, if none of the above situations are true, it means our string length is less than our truncation
num
. Therefore, we can just return the string.
function truncateString(str, num) {
if (str.length <= num) {
return str;
} else {
return str.slice(0, num > 3 ? num - 3 : num) + '...';
}
}
🚀 Run Code
- First we need an if-statement to test if the length of the full string passed in as the first argument already fits within the size limit passed in as the second argument. If so we can just return the string that was passed in.
if (str.length <= num)
return str;
- If our
if
statement above fails, we move to theelse
, where we are going to return a "slice" of the string. The slice method extracts a section of a string and returns a new string. Here we pass 0 as the starting point for our slice. To determine the endpoint, we use a ternary operator:num > 3 ? num - 3 : num
. In our ternary, ifnum
is larger than 3, we must factor in the three dots to our total length, and thus we end our slice atnum-3
. If num is less than or equal to 3, our slice gets an end variable of justnum
. Finally, the'...'
is appended to the end of our new string and is returned.
} else {
return str.slice(0, num > 3 ? num - 3 : num) + '...';
}
-
NOTE In order to understand the above code, you need to understand how a Ternary Operator works. The Ternary Operator is frequently used as a shortcut for the
if
statement and follows this format:condition ? expr1 : expr2
. If thecondition
evaluates to true, the operator returns the value ofexpr1
. Otherwise, it returns the value ofexpr2
.
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