Hi I'm going to make a calculator and I want a +/- button. I want to get the latest *, -, +, / in the string and define whats the laststring.
For example:
str="2+3*13"
I want this to be split into:
strA="2+3*"
strB="13"
Another example:
str="3-2+8"
Should split into:
strA="3-2+"
strB="8"
Use lastIndexOf and one of the substring methods:
var strA, strB,
// a generic solution for more operators might be useful
index = Math.max(str.lastIndexOf("+"), str.lastIndexOf("-"), str.lastIndexOf("*"), str.lastIndexOf("/"));
if (index < 0) {
strA = "";
strB = str;
} else {
strA = str.substr(0, index+1);
strB = str.substr(index+1);
}
You can use replace, match, and Regular Expressions:
str="3-2+8"
strA = str.replace(/\d+$/, "")
strB = str.match(/\d+$/)[0]
console.log(str, strA, strB);
> 3-2+8 3-2+ 8
replace does not modify the str, so why not?
str variable is not modified in any way during this entire operation (as evident by the console.log at the end of the code block). The .replace() function is used specifically for the purpose of setting strA to the desired value.You can use regular expression and split method:
var parts = "2 + 4 + 12".split(/\b(?=\d+\s*$)/);
Will give you and array:
["2 + 4 + ", "12"]
Couple of tests:
"(2+4)*230" -> ["(2+4)*", "230"]
"(1232-74) / 123 " -> ["(1232-74) / ", "123 "]
"12 * 32" -> ["12 * ", "32"]
