Access Control String (ACS) Parser/Interpreter with PEG.js - javascript

Preface
I'm working on creating a Access Control String (or System) (ACS) string Parser/Interpreter with PEG.js. ACS strings are commonly used on Bulletin Board Systems (BBSs) to check access rights to particular areas of the board. For example, see Renegade's ACS documentation.
Example ACS Strings
Below are some simplified strings and their English translations for illustration:
// Has GM123 OR NOT GM456
GM123|!GM456
// Has GM123 OR NOT (GM456 AND GM789) (note: AND is implied in this grammar if not specified)
GM123|!(GM456GM789)
// Has GM123 AND NOT GM456 OR has GM789
GM123!GM456|GM789
// Has GM1 OR (NOT GM2 OR GM3)
GM1|(!GM2|GM3)
What I'm Trying to Achieve
What I would like to do here is parse and interpret (or "run") the ACS string and ultimately end up with a final boolean.
Grammar So Far
Below is the PEG.js grammer I've some up with so far. Note that the ACS strings themselves are a bit more complex than the examples above (I allow for example GM['abc','def']) but I think up to this point it's fairly self explanatory.
{
function checkAccessSingle(acsName, arg) {
return true;
}
function checkAccessMulti(acsName, args, anyMatch) {
return true;
}
function makeNot(not, x) {
return not ? !x : x;
}
}
start
= acsString
whitespaceChar
= ' '
ws
= whitespaceChar*
lineTerminatorChar
= [\r\n\u2028\u2029]
decimalDigit
= [0-9]
integer
= decimalDigit+ { return parseInt(text(), 10); }
asciiPrintableChar
= [ -~]
singleAsciiStringChar
= !("'") asciiPrintableChar { return text(); }
doubleAsciiStringChar
= !('"') asciiPrintableChar { return text(); }
nonEmptyStringLiteral
= "'" chars:singleAsciiStringChar+ "'" { return chars.join(''); }
/ '"' chars:doubleAsciiStringChar+ '"' { return chars.join(''); }
AND
= '&'
OR
= '|'
NOT
= '!'
acsName
= n:([A-Z][A-Z]) { return n.join(''); }
acsArg
= nonEmptyStringLiteral
/ integer
acsArgs
= first:acsArg rest:(ws ',' ws a:acsArg { return a; })* {
var args = [ first ];
for(var i = 0; i < rest.length; ++i) {
args.push(rest[i]);
}
return args;
}
singleAcsCheck
= not:NOT? n:acsName a:acsArg* {
return function() {
makeNot(not, checkAccessSingle(n, a));
}
}
/ not:NOT? n:acsName '[' a:acsArgs ']' {
return function() {
return makeNot(not, checkAccessMulti(n, a, false));
}
}
/ not:NOT? n:acsName '{' a:acsArgs '}' {
return function() {
return makeNot(not, checkAccessMulti(n, a, true));
}
}
multiAcsCheck
= singleAcsCheck+
acsString = multiAcsCheck
Where I Need Help
The main issue I'm having (if not others I haven't run into yet!) is handling precedence with () and the OR clauses. This may be something simple, but I've worked on this for days and have some up short. Again, what I'm ultimately attempting to achieve here is to feed in an ACS string and output a final boolean result. The various ACS "commands" (e.g. 'GM' in the above example) should make method calls that do the dirty work.

Here's a quick demo that parses your example input properly and shows how you could go about evaluating the expressions on the fly (which will return a boolean):
{
function check(name, value) {
// Dummy implementation: returns true when the name starts with 'A'
return name.charAt(0) == 'A';
}
}
start
= expr
expr
= or_expr
or_expr
= left:and_expr '|' right:expr { return left || right; }
/ and_expr
and_expr
= left:not_expr '&'? right:expr { return left && right; }
/ not_expr
not_expr
= '!' value:atom { return !value; }
/ atom
atom
= acs_check
/ '(' value:expr ')' { return value; }
acs_check
= n:name a:arg { return check(n, a); }
name
= c:([A-Z][A-Z]) { return c.join(''); }
arg
= c:[A-Z]+ { return c.join(''); }
/ d:[0-9]+ { return d.join(''); }

Related

How to get all the characters not contained in anchor tags using RegEx in Javascript?

How can I use regex to get an array of all the individual characters not contained within anchor tags?
So for example, with this text:
DOWNLOAD THIS OR THAT
I want an array of the indices for the characters D,O,W,N,L,O,A,D, ,T,H,I,S, , ... etc.
I managed to figure out how to get everything I don't want selected, using this: /(?:<.*?>)
But I don't know how to use that to get all the characters outside of that group.
As already pointed out by #Cid, don't do this with regular expressions. Instead, use something like below and read the input character by character:
function reader(el) {
let i = 0;
let src = el.innerHTML;
const r = {
done() {
return i >= src.length;
},
advance() {
i += 1;
},
char() {
let c = !r.done() ? src[i] : '';
r.advance();
return c;
},
peek() {
return !r.done() ? src[i] : '';
}
};
return r;
}
function collector(el) {
const r = reader(el);
const skipUntil = char => {
while (r.peek() !== char) {
r.advance();
}
r.advance();
};
return {
collect() {
const v = [];
while (!r.done()) {
if (r.peek() === '<') {
skipUntil('>');
} else if (r.peek() === '\n') {
r.advance();
} else {
v.push(r.char());
}
}
return v;
}
};
}
/* --- */
const el = document.querySelector('#source');
const cl = collector(el);
console.log(cl.collect());
<div id="source">
DOWNLOAD THIS OR THAT
</div>

Javascript issue with precedence

I have built this function to replace a group of characters in a string by a random value from another list within a function:
function replaceExpr(a) {
var expToReplace = 0
var newSent = a
while (expToReplace == 0) {
if (a.search("zx") == -1) {
expToReplace = 1
} else {
var startPos = a.search("zx");
startPos += 2;
var endPos = a.search("xz");
var b = a.substring(startPos, endPos);
var fn = window[b];
if (typeof fn === "function") var newWord = fn();
final = newSent.replace("zx" + b + "xz", newWord);
newSent = final
a = a.replace("zx" + b + "xz", "")
}
}
return final
}
function appearance() {
var list = [
"attractive",
"fit",
"handsome",
"plain",
"short",
"tall",
"skinny",
"well-built",
"unkempt",
"unattractive"
]
return list[Math.floor(Math.random() * list.length)];
}
function personality() {
var list = [
"aggresive",
"absent-minded",
"cautious",
"detached from the real world",
"easygoing",
"focused",
"honest",
"dishonest",
"polite",
"uncivilized"
]
return list[Math.floor(Math.random() * list.length)];
}
An example :
var a = replaceExpr("Theodor is a zxappearancexz man. He seems rather zxpersonalityxz.")
alert(a)
// Theodor is a unattractive man. He seems rather cautious.
Everything works perfectly with the function but I have an issue related to it. As you can see, there's one grammar mistake : it's written "a unattractive" where it should be "an unattractive".
There's a function I usually use to to fix the a\an issue which is :
var AvsAnSimple = (function (root) {
//by Eamon Nerbonne (from http://home.nerbonne.org/A-vs-An), Apache 2.0 license
// finds if a word needs a "a" or "an" before it
var dict = "2h.#2.a;i;&1.N;*4.a;e;i;o;/9.a;e;h1.o.i;l1./;n1.o.o;r1.e.s1./;01.8;12.1a;01.0;12.8;9;2.31.7;4.5.6.7.8.9.8a;0a.0;1;2;3;4;5;6;7;8;9;11; .22; .–.31; .42; .–.55; .,.h.k.m.62; .k.72; .–.82; .,.92; .–.8;<2.m1.d;o;=1.=1.E;#;A6;A1;A1.S;i1;r1;o.m1;a1;r1; .n1;d1;a1;l1;u1;c1.i1.a1.n;s1;t1;u1;r1;i1;a1;s.t1;h1;l1;e1;t1;e1.s;B2.h2.a1.i1;r1;a.á;o1.r1.d1. ;C3.a1.i1.s1.s.h4.a2.i1.s1;e.o1.i;l1.á;r1.o1.í;u2.i;r1.r1.a;o1.n1.g1.j;D7.a1.o1.q;i2.n1.a1.s;o1.t;u1.a1.l1.c;á1. ;ò;ù;ư;E7;U1;R.b1;o1;l1;i.m1;p1;e1;z.n1;a1;m.s1;p5.a1.c;e;h;o;r;u1.l1;o.w1;i.F11. ;,;.;/;0;1;2;3;4;5;6;71.0.8;9;Ae;B.C.D.F.I2.L.R.K.L.M.N.P.Q.R.S.T.B;C1;M.D;E2.C;I;F1;r.H;I3.A1;T.R1. ;U;J;L3.C;N;P;M;O1. ;P1;..R2.A1. ;S;S;T1;S.U2.,;.;X;Y1;V.c;f1.o.h;σ;G7.e1.r1.n1.e;h1.a3.e;i;o;i1.a1.n1.g;o2.f1. ;t1.t1. ;r1.i1.a;w1.a1.r1.r;ú;Hs. ;&;,;.2;A.I.1;2;3;5;7;B1;P.C;D;F;G;H1;I.I6;C.G.N.P.S1.D;T.K1.9;L;M1;..N;O2. ;V;P;R1;T.S1.F.T;V;e2.i1.r;r1.r1.n;o2.n6;d.e1.s;g.k.o2;l.r1;i1.f;v.u1.r;I3;I2;*.I.n1;d1;e1;p1;e1;n1;d2;e1;n1;c1;i.ê.s1;l1;a1;n1;d1;s.J1.i1.a1.o;Ly. ;,;.;1;2;3;4;8;A3. ;P;X;B;C;D;E2. ;D;F1;T.G;H1.D.I1.R;L;M;N;P;R;S1;m.T;U1. ;V1;C.W1.T;Z;^;a1.o1.i1.g;o1.c1.h1.a1;b.p;u1.s1.h1;o.ộ;M15. ;&;,;.1;A1;.1;S./;1;2;3;4;5;6;7;8;Ai;B.C.D.F.G.J.L.M.N.P.R.S.T.V.W.X.Y.Z.B1;S1;T.C;D;E3.P1;S.W;n;F;G;H;I4. ;5;6;T1;M.K;L;M;N;O1.U;P;Q;R;S;T1;R.U2. ;V;V;X;b1.u1.m;f;h;o2.D1.e.U1;..p1.3;s1.c;Ny. ;+;.1.E.4;7;8;:;A3.A1;F.I;S1.L;B;C;D;E3.A;H;S1. ;F1;U.G;H;I7.C.D1. ;K.L.N.O.S.K;L;M1;M.N2.R;T;P1.O1.V1./1.B;R2;J.T.S1;W.T1;L1.D.U1.S;V;W2.A;O1.H;X;Y3.C1.L;P;U;a1.s1.a1.n;t1.h;v;²;×;O5;N1;E.l1;v.n2;c1.e.e1.i;o1;p.u1;i.P1.h2.i1.a;o2.b2;i.o.i;Q1.i1.n1.g1.x;Rz. ;&;,;.1;J./;1;4;6;A3. ;.;F1;T.B1;R.C;D;E3. ;S1.P;U;F;G;H1.S;I2.A;C1. ;J;K;L1;P.M5;1.2.3.5.6.N;O2.H;T2;A.O.P;Q;R1;F.S4;,...?.T.T;U4;B.M.N.S.V;X;c;f1;M1...h2.A;B;ò;S11. ;&;,;.4.E;M;O;T1..3.B;D;M;1;3;4;5;6;8;9;A3. ;8;S2;E.I.B;C3.A1. ;R2.A.U.T;D;E6. ;5;C3;A.O.R.I1.F.O;U;F3;&.H.O1.S.G1;D.H3.2;3;L;I2. ;S1.O.K2.I.Y.L3;A2. ;.;I1. ;O.M3;A1. ;I.U1.R.N5.A.C3.A.B.C.E.F.O.O5. ;A1.I;E;S1;U.V;P7;A7;A.C.D.M.N.R.S.E1. ;I4;C.D.N.R.L1;O.O.U.Y.Q1. ;R;S1;W.T9.A1. ;C;D;F;I;L;M;S;V;U7.B.L.M.N.P.R.S.V;W1.R;X1.M;h1.i1.g1.a1.o;p1.i1.o1;n.t2.B;i1.c1.i;T4.a2.i2.g1.a.s1.c;v1.e1.s;e1.a1.m1.p;u1.i2.l;r;à;Um..1.N1..1.C;/1.1;11. .21.1;L1.T;M1.N;N4.C1.L;D2. .P.K;R1. .a;b2;a.i.d;g1.l;i1.g.l2;i.y.m;no. ;a1.n.b;c;d;e1;s.f;g;h;i2.d;n;j;k;l;m;n;o;p;q;r;s;t;u;v;w;p;r3;a.e.u1.k;s3. ;h;t1;r.t4.h;n;r;t;x;z;í;W2.P1.:4.A1.F;I2.B;N1.H.O1.V;R1.F1.C2.N.U.i1.k1.i1.E1.l1.i;X7;a.e.h.i.o.u.y.Y3.e1.t1.h;p;s;[5.A;E;I;a;e;_2._1.i;e;`3.a;e;i;a7; .m1;a1;r1. .n1;d2; .ě.p1;r1;t.r1;t1;í.u1;s1;s1;i1. .v1;u1;t.d3.a1.s1. ;e2.m1. ;r1. ;i2.c1.h1. ;e1.s1.e2.m;r;e8;c1;o1;n1;o1;m1;i1;a.e1;w.l1;i1;t1;e1;i.m1;p1;e1;z.n1;t1;e1;n1;d.s2;a1. .t4;a1; .e1; .i1;m1;a1;r.r1;u1.t.u1.p1. ;w.f3. ;M;y1.i;h9. ;,;.;C;a1.u1.t1;b.e2.i1.r1;a.r1.m1.a1.n;o4.m2.a1; .m;n8; .b.d.e3; .d.y.g.i.k.v.r1.s1. ;u1.r;r1. ;t1;t1;p1;:.i6;b1;n.e1;r.n2;f2;l1;u1;ê.o1;a.s1;t1;a1;l1;a.r1; .s1; .u.k1.u1. ;l3.c1.d;s1. ;v1.a;ma. ;,;R;b1.a.e1.i1.n;f;p;t1.a.u1.l1.t1.i1.c1.a1.m1.p1.i;×;n6. ;V;W;d1; .t;×;o8;c2;h1;o.u1;p.d1;d1;y.f1; .g1;g1;i.no. ;';,;/;a;b;c1.o;d;e2.i;r;f;g;i;l;m;n;o;r;s;t;u;w;y;z;–;r1;i1;g1;e.t1;r1.s;u1;i.r3. ;&;f;s9.,;?;R;f2.e.o.i1.c1.h;l1. ;p2.3;i1. ;r1.g;v3.a.e.i.t2.A;S;uc; ...b2.e;l;f.k2.a;i;m1;a1. .n3;a3; .n5.a;c;n;s;t;r1;y.e2; .i.i8.c2.o1.r1.p;u1.m;d1;i1.o;g1.n;l1.l;m1;o.n;s1.s;v1.o1;c.r5;a.e.i.l.o.s3. ;h;u1.r2;e.p3;a.e.i.t2.m;t;v.w1.a;xb. ;';,;.;8;b;k;l;m1;a.t;y1. ;y1.l;{1.a;|1.a;£1.8;À;Á;Ä;Å;Æ;É;Ò;Ó;Ö;Ü;à;á;æ;è;é1;t3.a;o;u;í;ö;ü1; .Ā;ā;ī;İ;Ō;ō;œ;Ω;α;ε;ω;ϵ;е;–2.e;i;ℓ;";
function fill(node) {
var kidCount = parseInt(dict, 36) || 0,
offset = kidCount && kidCount.toString(36).length;
node.article = dict[offset] == "." ? "a" : "an";
dict = dict.substr(1 + offset);
for (var i = 0; i < kidCount; i++) {
var kid = node[dict[0]] = {}
dict = dict.substr(1);
fill(kid);
}
}
fill(root);
return {
raw: root,
//Usage example: AvsAnSimple.query("example")
//example returns: "an"
query: function (word) {
var node = root, sI = 0, result, c;
do {
c = word[sI++];
} while ('"‘’“”$\''.indexOf(c) >= 0);//also terminates on end-of-string "undefined".
while (1) {
result = node.article || result;
node = node[c];
if (!node) return result;
c = word[sI++] || " ";
}
}
};
})({})
Now, the problem is that I can't find a way to use this function in conjunction with the replaceExpr. The following obviously wouldn't work because of order precedence :
var a = replaceExpr("Theodor is " + AvsAnSimple(zxappearancexz) + "man. He seems rather " + AvsAnSimple(zxpersonalityxz).")
I just recently started learning javascript so my knowledge is rather limited. Any ideas how I could overcome this?
Thank you!
You could use a regular expression to optionally match the " a " or "an" before your word in the input string and store that matched portion in a variable using the String.match() function, then check if that " a " or " an " exists in your matched string, do the manipulations you need to do and store that manipulated string in a separate variable, then use String.replace() to find that previously matched string again, and replace it wit
your manipulated string. The regular expression you could use for this is /(\san?\s)?(zx\w*zx)/gm
See the regular expression here for more context.
Thank you Joseph! With your help I managed to find something that works by using your regular expression. Here's my function :
function replaceExpr(a) {
var nbExprToReplace = 1;
while (nbExprToReplace == 1) {
if (a.search("zx") == -1) {
nbExprToReplace = 0;
} else {
var currentGroup = a.match(/(\san?\s)?(zx\w*xz)/);
var exprToChange = currentGroup[2];
exprToChange = exprToChange.slice(2,-2);
var exprToChange = window[exprToChange];
if (typeof exprToChange !== "function") {
alert("the keyword is not a recognized function!");
break;
} else {
exprToChange = exprToChange();
var final = exprToChange
};
if (currentGroup[1] === undefined) {
} else {
var newArticle = AvsAnSimple.query(exprToChange);
final = newArticle.concat(" " + final)
};
a = a.replace(currentGroup[0], " " + final);
};
};
return a;
};

Variable substitution within a string

I'm trying to come up with some very reusable code that will look up and perform variable substitutions within a string.
The example string below contains a $$ reference to a variable. Format is varname.key.
I want the subText() function to be reusable. The issue I'm having is repvars themselves can require substitution. The code hasn't finished substituting the example text and I'm asking it to substitute the repvars.cr by calling the same function. This seems to through it off. I'm saying that because if I do it separately in works.
var exampleText = "A string of unlimited length with various variable substitutions included $$repvars.cr$$";
var repvars = {
cr: 'Copyright for this is $$repvars.year$$',
year: '2019'
}
function subText(text) {
var subVars = findSubs(text);
return makeSubs(text, subVars);
}
function findSubs(theText) {
var subarr = [];
while (theText.indexOf('$$') > -1) {
theText = theText.substring(theText.indexOf('$$') + 2);
subarr.push(theText.substring(0, theText.indexOf('$$')));
theText = theText.substring(theText.indexOf('$$') + 2);
}
return subarr;
}
function makeSubs(text, subs) {
for (var s = 0; s < subs.length; s++) {
var subst = getSubVal(subs[s]);
text = text.split("$$" + subs[s] + "$$").join(subst);
}
return text;
}
function getSubVal(subvar) {
var subspl = subvar.split('.');
switch (subspl[0]) {
default:
return processRepVar(subspl[1]);
}
}
function processRepVar(rvName) {
var data = getRepVarData(rvName);
if(data.indexOf('$$') > -1) {
subText(data);
} else {
return data;
}
}
function getRepVars() {
return repvars;
}
function getRepVarData(key) {
return getRepVars()[key];
}
subText(exampleText);
Aren't you just missing a return here?
function processRepVar(rvName) {
var data = getRepVarData(rvName);
if(data.indexOf('$$') > -1) {
subText(data);
} else {
return data;
}
}
Changing subText(data) to return subText(data); makes your code work for me.
Working jsfiddle: https://jsfiddle.net/uzxno754/
Have you tried regular expressions for this?
function replace(str, data) {
let re = /\$\$(\w+)\$\$/g;
while (re.test(str))
str = str.replace(re, (_, w) => data[w]);
return str;
}
//
var exampleText = "A string with variables $$cr$$";
var repvars = {
cr: 'Copyright for this is $$year$$',
year: '2019'
}
console.log(replace(exampleText, repvars))
Basically, this repeatedly replaces $$...$$ things in a string until there are no more.

What is best way to replace %[variable, percentage] with (variable*percentage)/100 in string?

I have string where there may be occurrence of %[{variable}, percentage] which i want to convert to (({variable}*percentage)/100) and replace it at same location. What is best way to do it?
Example: {operation} + %[{cost}, 10] should be converted to {operation} + (({cost}*10)/100)
I tried following but it didn't work:
function Service(){
this.percentageRegx = "\%\[(.*?)]";
this.percentageVariableRegx = "\%\[(.*?)]";
this.percentageValueRegx = "\,(.*?)]";
this.getPercentageFromFormula = function (formula) {
var data = [];
try {
do {
m = self.percentageRegx.exec(formula);
if (m) {
var variableData = self.percentageVariableRegx.exec(m[1]),
percentageData = self.percentageValueRegx.exec(m[1]);
if(variableData !== null && percentageData !== null){
data.push({
string: m[1],
variable: variableData[1],
percentage: percentageData[1]
});
}
}
} while (m);
} catch (e) {}
return data;
};
/**
* Convert percentages to formula
*/
this.replacePercentageToFormula = function (formula) {
var percentages = self.getPercentageFromFormula(formula);
angular.forEach(percentages, function (percentage) {
formula.replace(percentage.string,"(("+percentage.variable+"*"+percentage.percentage+")/100)");
});
return formula;
};
}
var service = new Service();
formula = service.replacePercentageToFormula("{operation} + %[{cost}, 10]");
It giving me Uncaught SyntaxError: Invalid or unexpected token error
That's a lot of code for what seems to me like a simple one-line regex-based string replacement:
var input = "{operation} + %[{cost}, 10] {?} * %[{123}, 5]";
var output = input.replace(/%\[(\{[^}]+\}), *(\d+)\]/g, "(($1*$2)/100)");
console.log(output);
I suggest you to implement a very very basilar template engine, or, if you need for many and solid features, have a look at one existing such as HandleBars, or TwigJS.
By the way, this is a little implementation:
var Template = (function() {
function TemplateEngine() {
this._re = (function(start, end) {
start = "\\" + start.split("").join("\\");
end = "\\" + end.split("").join("\\");
return new RegExp(
"(("+ start +")(.*)("+ end +"))",
"g"
);
}).apply(this, this.separators);
}
TemplateEngine.prototype.separators = ["{{", "}}"];
TemplateEngine.prototype.map = function(str, model) {
return str
.replace(this._re,
function(matches, tpl, sStart, content, sEnd) {
return Object.keys(model).reduce(function(res, variable) {
return (
res = content.replace(variable, model[variable])
);
}, "");
}
);
}
TemplateEngine.prototype.render = function(tpl, context) {
var parsed = this.map(tpl, context), result;
try {
result = eval(parsed);
} catch(e) {
result = parsed.replace(/['"`]/g, "");
}
this._re.lastIndex = 0;
return result;
};
return new TemplateEngine();
})();
// TESTS
console.log(
Template.render("{{foo * 5}}", {foo: 2})
);
console.log(
Template.render("{{foo 'World'; }}", {foo: "Hello"})
);
NOTE: I always suggest you to use a community-trusted solution.

Evaluate string expression using Javascript or jQuery

I have to evaluate expressions like below, which are available in string variable, without using eval or external libraries or third party packages:
"abs(add(multiply(-1,multiply(-1,subtract(89,19880))),subtract(add(12,add(247,45986)),98)))"
Can anyone suggest how it can be done using Javascript or jQuery?
add(expr1,expr2) - takes two operands and returns their sum.
subtract(expr1,expr2) - takes two operands and returns their difference (expr1 - expr2).
multiply(expr1,expr2) - takes two operands and returns their product.
abs(expr1) - takes one operand and returns its absolute value.
Implement the traditional way of expression evaluation using stacks - operand stack, operator stack. Push-pop from the stacks. That's the best way I can think of.
I did not really bother making the code efficient or bullet proof (there are probably some bugs in here), but here's an example on how you could do it. You could convert your infix expression to a postfix representation as a tokens array and then perform the evaluation of that postfix representation.
NOTE: I did not allow for expressions with spaces to be correctly tokenized, but you could change this if that's not what you need.
var logEl = document.getElementById('log'),
expInput = document.querySelector('input');
document.querySelector('button').addEventListener('click', function () {
updateEvaluationResult(expInput.value);
});
updateEvaluationResult(expInput.value);
function updateEvaluationResult(exp) {
var logMsg;
try { logMsg = evaluateExpression(exp); }
catch (e) {
logMsg = e.message + ('charIndex' in e? ' (char index ' + e.charIndex + ')' : '')
}
logEl.textContent = logMsg;
}
function evaluateExpression(exp) {
var functions = {
abs: Math.abs,
multiply: function(num1, num2) {
return num1 * num2;
},
substract: function(num1, num2) {
return num1 - num2;
},
add: function(num1, num2) {
return num1 + num2;
}
};
return (evaluateExpression = function(exp) {
var fn;
return postfixTokenizationOf(exp).reduce(function(resultStack, token) {
if (typeof token == 'number') resultStack.push(token);
else {
fn = functions[token];
if (!fn) throw new Error("'" + token + "' is an invalid function");
resultStack.push(functions[token].apply(
null,
resultStack.splice(resultStack.length - fn.length)
));
}
return resultStack;
}, []).pop();
})(exp);
}
function postfixTokenizationOf(exp) {
if (!exp) return [];
var stack = [],
output = [],
indexOf = [].indexOf,
tokenRx = /[^-(),\d]+|[(),]|[-\d]+/g,
functionTokenRx = /[^-(),\d]+/,
charTokenHandlers = {
'(': stack.push.bind(stack, '('),
')': handleRightParenthesis,
',': handleArgSeperator
},
charTokenHandler, token, match;
while (match = tokenRx.exec(exp)) {
token = match[0];
if ((charTokenHandler = charTokenHandlers[token])) {
charTokenHandler();
continue;
}
if (isNumeric(token)) {
output.push(+token);
continue;
}
handleFunction();
}
if (popStackUntilOneOfTokenFound('()')) throwMismatchedParenthesisError();
return output;
function handleFunction() {
var nextCharIndex = tokenRx.lastIndex;
if (exp[nextCharIndex] != '(') throwError('expected a function call');
else stack.push(token);
}
function handleRightParenthesis() {
if (!popStackUntilOneOfTokenFound('(')) throwMismatchedParenthesisError();
stack.pop();
if (isFunction(topOfStack())) output.push(stack.pop());
}
function handleArgSeperator() {
if (!popStackUntilOneOfTokenFound('(')) throwError(
'mismatched parenthesis or misplaced argument seperator'
);
}
function popStackUntilOneOfTokenFound(tokenChars) {
var t;
while (indexOf.call(tokenChars, t = topOfStack()) == -1 && t) output.push(stack.pop());
return !!stack.length;
}
function throwError(msg) {
var err = new Error(msg);
err.charIndex = tokenRx.lastIndex;
throw err;
}
function throwMismatchedParenthesisError() {
throwError('mismatched parenthesis');
}
function topOfStack() {
return stack[stack.length - 1];
}
function isFunction(token) {
return functionTokenRx.test(token);
}
function isNumeric(token) {
return parseFloat(token) == token;
}
}
input {
width: 500px;
}
<label>Exp:
<input type="text" value="abs(add(multiply(-1,multiply(-1,substract(89,19880))),substract(add(12,add(247,45986)),98)))">
</label>
<div id="log"></div>
<button>Evaluate</button>
The easiest way to do this is to create a bunch of functions that do what you want, then eval() the code.
function calc(str){
function subtract(a, b){
return a-b;
}
function add(a, b){
return a+b;
}
function mulitiply(a, b){
return a*b;
}
function divide(a, b){
return a/b;
}
function abs(a){
return Math.abs(a);
}
return eval('('+str+')');
}
console.log(calc('abs(add(multiply(-1,multiply(-1,subtract(89,19880))),subtract(add(12,add(247,45986)),98)))'));
How about to write your custom functions?
function add(ad1, ad2) {
var sum = parseFloat(ad1) + parseFloat(ad2);
return sum;
}
function subtract(sub1, sub2) {
var sub = parseFloat(sub1) - parseFloat(sub2);
return sub;
}
function multiply(mlt1, mlt2) {
var mlt = parseFloat(mlt1) * parseFloat(mlt2);
return mlt;
}
function abs(ab1) {
var abs = Math.abs(parseFloat(ab1));
return abs;
}
function evaluatethis(exp) {
document.write('<script>alert(' + exp + ');</' + 'script>');
}
evaluatethis("abs(add(multiply(-1,multiply(-1,subtract(89,19880))),subtract(add(12,add(247,45986)),98)))");

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