如何在Javascript中为每个索引将数组拆分为多个数组

Question

I'm trying to split a string by whitespace.

var conditionSplit = "item == 2 item !== 1 item <= 5".match(/\S+/g);

It will give output like:

// ["item", "==", "2", "item", "!==", "1", "item", "<=", "5"];

I need the result to be like:

// [["item","==","2"],["item","!==","1"],["item","<=","5"]]

What should I do to split that array or going from the first result.

Thanks for help.

Answer 1

If your sample output is an error and you really want an array of arrays, where each of the subordinate arrays is three entries long, you can do that by using forEach and pushing a new array onto a result array whenever the index you're visiting is evenly divisible by 3:

 var conditionSplit = "item == 2 item !== 1 item <= 5".match(/\\S+/g); var result = []; var current; conditionSplit.forEach(function(entry, index) { if (index % 3 == 0) { current = []; result.push(current); } current.push(entry); }); snippet.log(JSON.stringify(result)); 

 <!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 --> <script src="//tjcrowder.github.io/simple-snippets-console/snippet.js"></script> 

Or if you wanted to do it by detecting the item string, you just change if (index % 3 == 0) to if (entry == "item") :

 var conditionSplit = "item == 2 item !== 1 item <= 5".match(/\\S+/g); var result = []; var current; conditionSplit.forEach(function(entry) { if (entry == "item") { current = []; result.push(current); } current.push(entry); }); snippet.log(JSON.stringify(result)); 

 <!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 --> <script src="//tjcrowder.github.io/simple-snippets-console/snippet.js"></script> 

...but you said you wanted to do it by index, so...

Answer 2

You could try to match by non-whitespace/whitespace tuples and then add a quantifier:

([^\S]+\S*){3}

This will leave you with whitespace at the end of the 3rd element though, so trimming may be required

Answer 3

This can be solved using Array.prototype.reduce :

 // This variable will contain the "array of arrays", where each // index will be an array of each expression as you requested... var allResults = []; "item == 2 item !== 1 item <= 5" .match(/\\S+/g) .reduce(function(result, next) { // Whenever an "item" string is detected, this starts // a new array item if (next == "item") { result = []; allResults.push(result); } result.push(next); return result; }, null); alert(JSON.stringify(allResults)); 

Are you looking for parsing JavaScript?

If you're looking for parsing JavaScript, you should take a look at Esprima and use an abstract syntax tree to analyze expressions programmatically.

For example, if you split your string by "item" , and you parse every expression, you would get something like the following AST:

// item == 2 would be:

{
    "type": "Program",
    "body": [
        {
            "type": "ExpressionStatement",
            "expression": {
                "type": "BinaryExpression",
                "operator": "==",
                "left": {
                    "type": "Identifier",
                    "name": "item"
                },
                "right": {
                    "type": "Literal",
                    "value": 2,
                    "raw": "2"
                }
            }
        }
    ],
    "sourceType": "script"
}

It sounds complicated, but parsing makes things easier once you get into it! You can play with Esprima using its online parser demo .

Answer 4

You could try to match item followed by =!<0-9 and split each element.

 var sa = "item == 2 item !== 1 item <= 5".match(/item[ =!<0-9]+/g);
        var n = sa.length;
        var ar = new Array(n);
        for (i = 0; i < n; i++) ar[i] = sa[i].split(" ");
        document.getElementById('fg').innerHTML = ar;