How to split "sTest_Val_1 < 50" string to "sTest_Val_1", "<", "50"

Question

I want to get a True or False value by putting a value in the sTest_Val_1 ("30") variable.

So we try to split and separate variables and operators.

At first I used the following source code.

However, this source code has caused problems because it is also splitting "_" from sTest_Val_1.

I could not split properly because of special characters in variables. So I could not put a value of "30" into the variable.

 var expression = "sTest_Val_1 < 50";  //or "sTest_Val_1<50"
 var copy = expression; //"sTest_Val_1 < 50"

 expression = expression.replace(/[0-9a-zA-Z]+/g, "#");  //"#_#_# < #"
 var numbers = copy.split(/[^0-9a-zA-Z\.]+/); //[sTest,Val,1,50]
 var operators = expression.split("#").filter(function (n) { return n }); //[_,_, < ]
 var result = [];
 var sRst = "";

 result.push(numbers[i]);
 sRst += numbers[i];
 if (i < operators.length) {
    result.push(operators[i]);
    sRst += operators[i];

 console.log(sRst);  
 return eval(sRst);  // I want True, False

The value of sTest_Val_1 is defined in another page. (i get this value to javascript object when first page loaded.)

string sTest_Val_1 = "30";
string sTest_Val_2 = "30";
string sTimeVal_1 = "65380";
// ....

"sTest_Val_1" This value can only contain alphabetic characters in the first character.

However, the length of the characters is random, and the special characters in the characters are also random. (<,>, +, -, and = are not included.)

My English is not good enough. Please understand.

Before you split you regex the expression to catch the operator. — Laurent Mesguen, Jun 20 '17 at 07:07

Alexandru Severin · Accepted Answer · 2017-06-20T07:50:49.157

0

You can use RegEx to find the position of the operator, without knowing the exact operator. /<|>|\+|\-|=|&&/ will match <, >, +, = or &&

var expression = "sTest_Val_1 < 50";  //or "sTest_Val_1<50"
var regResult = /<|>|\+|\-|=|&&/.exec(expression); //match <, >, +, = or &&
if(!regResult.length){ //regResult is an array containing the operators found
   // handle no operator found
}
var opIdx = regResult.index; //the index of the first found operator
var op = regResult[0];
var variable = expression.substring(0, opIdx).trim(); //split until operator and trim whitespaces
var value = expression.substring(opIdx + op.length, expression.length).trim(); //split after operator and trim whitespaces

Note: if you are expecting multiple operators in the expression, you should probably loop through regResult and do some modifications to the substring arguments.

Also, using eval is a bad ideea, I would recommend you to do a switch on the operator and check the condition properly for returning the result of the operation.

edited Jun 20 '17 at 07:50

answered Jun 20 '17 at 07:17

Alexandru Severin

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Thanks! Also, thanks for letting me know that eval is a bad idea. You mean use switch ? – cherryJang Jun 20 '17 at 07:28
@cherryJang I'm not exactly sure what you're trying to evaluate, but if you can resort to using switch and/or ifs, you should. – Alexandru Severin Jun 20 '17 at 07:32
oh! also "sTest_Val_1<50 && sTest_Val_2<50" this can possible? – cherryJang Jun 20 '17 at 07:33
Of course, just add it all operators to the regEx with `|` between them ( `/<|>|\+|\-|=|&&/`). But you'll have to take into account the length of the operator when doing the substrings (updated answer) – Alexandru Severin Jun 20 '17 at 07:37

score 0 · Answer 2 · answered Jun 20 '17 at 10:36

0

You can split by operator (with keeping the operator) with capturing group.

expression = "sTest_Val_1 < 50"
expression.split(/(<|>|\+|\-|=|&&)/)

will result in ["sTest_Val_1 ", "<", " 50"]

answered Jun 20 '17 at 10:36

Fallenhero

1,563
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Oh Thanks for your answer! This also helpful. – cherryJang Jun 21 '17 at 07:50

How to split "sTest_Val_1 < 50" string to "sTest_Val_1", "<", "50"

2 Answers2