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Here is what's wrong with your code:

• Do not use variable names like _o. Get an editor with good auto-completion.

• typeof _o != 'object' does not do what you think it does: typeof([1,2]) // "object". In general, doing those kinds of checks is a code smell.

• if (!isNaN(parseInt(loc))) loc = parseInt(loc);. Confusing and not needed.
  JavaScript: ['a', 'b']["1"] // 'b'. Same goes for the other isNaN

• in. Do not do that check. null is a value, but what you want to return is the lack of value. It is undefined in JavaScript, and it is what will be returned if there is no value.

• Consider using split instead of indexOf and substring. It is much faster and makes the code more readable.

So, here is a neat version for you:

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    // split chain on array and property accessors
    chain = chain.split(/[.\[\]]+/);             
    // traverse 1 level less when assigning; remove trailing ']' from split 
    var n = chain.length - assigning - !chain[n - 1]; 
    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];
        // if (data === undefined) return; // uncomment to handle bad chain keys      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)

Here is what's wrong with your code:

• Do not use variable names like _o. Get an editor with good auto-completion.

• typeof _o != 'object' does not do what you think it does: typeof([1,2]) // "object". In general, doing those kinds of checks is a code smell.

• if (!isNaN(parseInt(loc))) loc = parseInt(loc);. Confusing and not needed.
  JavaScript: ['a', 'b']["1"] // 'b'. Same goes for the other isNaN

• in. Do not do that check. null is a value, but what you want to return is the lack of value. It is undefined in JavaScript, and it is what will be returned if there is no value.

• Consider using split instead of indexOf and substring. It is much faster and makes the code more readable.

So, here is a neat version for you:

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    // split chain on array and property accessors
    chain = chain.split(/[.\[\]]+/);       
    // remove trailing ']' from split   
    if (!chain[chain.length - 1]) chain.pop();
    // traverse 1 level less when assigning
    var n = chain.length - assigning; 
    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];
        // if (data === undefined) return; // uncomment to handle bad chain keys      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)

Here is what's wrong with your code:

• Do not use variable names like _o. Get an editor with good auto-completion.

• typeof _o != 'object' does not do what you think it does: typeof([1,2]) // "object". In general, doing those kinds of checks is a code smell.

• if (pos === -1). Do not use strict comparison unless it's meaningful. Embrace the language.

• if (!isNaN(parseInt(loc))) loc = parseInt(loc);. Confusing and not needed.
  JavaScript: ['a', 'b']["1"] // 'b'. Same goes for the other isNaN

• in. Do not do that check. null is a value, but what you want to return is the lack of value. It is undefined in JavaScript, and it is what will be returned if there is no value.

• Consider using split instead of your indexOf and substring. It is much faster and makes the code more readable.

So, here is a neat version for you:

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    chain = chain.split(/[.\[\]]+/);     
    var n = chain.length;
    n = n - assigning - !chain[n - 1]; // trailing ']' in chain and assigning

    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];
        // if (data === undefined) return; // uncomment to handle bad chain keys      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)

Here is what's wrong with your code:

• Do not use variable names like _o. Get an editor with good auto-completion.

• typeof _o != 'object' does not do what you think it does: typeof([1,2]) // "object". In general, doing those kinds of checks is a code smell.

• if (!isNaN(parseInt(loc))) loc = parseInt(loc);. Confusing and not needed.
  JavaScript: ['a', 'b']["1"] // 'b'. Same goes for the other isNaN

• in. Do not do that check. null is a value, but what you want to return is the lack of value. It is undefined in JavaScript, and it is what will be returned if there is no value.

• Consider using split instead of indexOf and substring. It is much faster and makes the code more readable.

So, here is a neat version for you:

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    // split chain on array and property accessors
    chain = chain.split(/[.\[\]]+/);             
    // traverse 1 level less when assigning; remove trailing ']' from split 
    var n = chain.length - assigning - !chain[n - 1]; 
    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];
        // if (data === undefined) return; // uncomment to handle bad chain keys      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)

Here is a fast clean version for you

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    chain = chain.split(/[.\[\]]+/);     
    var n = chain.length;
    n = n - assigning - !chain[n - 1]; // trailing ']' in chain and assigning

    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)

Here is what's wrong with your code:

• Do not use variable names like _o. Get an editor with good auto-completion.

• typeof _o != 'object' does not do what you think it does: typeof([1,2]) // "object". In general, doing those kinds of checks is a code smell.

• if (pos === -1). Do not use strict comparison unless it's meaningful. Embrace the language.

• if (!isNaN(parseInt(loc))) loc = parseInt(loc);. Confusing and not needed.
  JavaScript: ['a', 'b']["1"] // 'b'. Same goes for the other isNaN

• in. Do not do that check. null is a value, but what you want to return is the lack of value. It is undefined in JavaScript, and it is what will be returned if there is no value.

• Consider using split instead of your indexOf and substring. It is much faster and makes the code more readable.

So, here is a neat version for you:

function chained(obj, chain, value){
    var assigning = (value !== undefined);
    chain = chain.split(/[.\[\]]+/);     
    var n = chain.length;
    n = n - assigning - !chain[n - 1]; // trailing ']' in chain and assigning

    for (var i = 0, data = obj; i < n; i++) {
        data = data[chain[i]];
        // if (data === undefined) return; // uncomment to handle bad chain keys      
    }

    if (assigning) {
        data[chain[n]] = value;
        return obj;
    } else {
        return data;       
    }
}

Blogged: http://glebm.blogspot.com/2011/01/javascript-chained-nested-assignment.html

Please come up with further improvements :)